DE2604298A1 - WET AND DRY FRICTION ELEMENTS - Google Patents

Description

1 BERLIN 33 - 1 - 8 MUNICH 80

Auguste-Viktoria-StraBe 65 _n ni | cpu | ^ CA PΔ PTM PP PlenzenauerstraBe 2

Pat. Dr. Ing. Ruechke "Γ. KUbOHM = & KAK I INtK PA-Anw. Dipl.-lng.

Pat. Dipl.-Ing. DATCMTAM \ A / XlTC ^Han * ^E · Rhk

oiaf Ruschke HAITNIANWALIT

Telephone: oeo / § I »g BERLIN - MÖNCHEN

Telegram address:

SÄ? 18,786

TELEX. 183788 TELEX: 522767

M 3662

Minnesota joining and ivianufacturing Company, Saint Paul, Minnesota, V.St.A.

Wet and dry friction elements

The invention relates to elastomeric fieibmasaen with improved Dimensional and low friction resistance ratios and on these elements containing them.

For many purposes it is essential that there is a suitable frictional resistance exists between two surfaces. The resistance must be in the form of a braking effect, a stopping effect or a switch-on or coupling effect appear, depending on the specific application in which he should go into action. E.g. switching on or coupling between two force-transmitting surfaces or a Stopping or braking take place in order to slide or slide on either a surface or a powered one

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V-belt or when starting and braking when transporting or walking.

Bicycle shoe brake pads represent a class of items which in particular are a combination of properties require. In a reasonable period of time, they must have a mass (rider plus bike plus load) of 50 to 110 kg or more, which moves at speeds of up to 90 km / h relative to the surface, safely stop. The slowing down and must stop under any conditions can be made. Bicycle brake pads are typical approximately parallelepiped shaped elastomeric blocks of about 10 χ 15 x 40 mm. They are mounted in a mechanical assembly so that the longitudinal surfaces of Block pairs are located on opposite wheel rims, namely a few millimeters away. The mechanical assembly is set up so that the blocks against the rim by an on Lever exerted force can be pressed by hand that are attached to the handlebar, the force being applied by a Transfer wire rope to suitable gripping or jaw devices will. The force can be momentary or continuous and relatively slight or suddenly strong to a rapid one To allow stopping to be exercised. A pair of brake pads is usually used for the rear and front wheels of the bike used.

The blocks typically consist of relatively solid blasto-

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meren. The braking surface of the block can be smooth, ie even,. or shaped, that is to say raised or indented. Although a large number of natural and synthetic blastomeres are available which could be suitably prepared to give a sufficiently high friction when the brake and wheel rim are dry, the coefficient of friction tends to approach zero, If the surfaces are wet, but on the other hand a sufficiently high wet friction is achieved, the dry friction becomes so high and braking takes place so quickly that the driver can lose control of the vehicle even after the slightest use of the brakes.

The invention is based on the object of providing friction elements To provide that with reasonable efficiency both are functional both wet and dry.

ils has been found that friction elements with very improved Properties related to the friction resistance Using a special class of blastomeres can be obtained may, as such, have an excessively high coefficient of friction

'would result in order to be generally applicable, but in combination

! nation with a friction modifying or reducing ^:

Medium, i.e. a solid lubricant, has a coefficient of friction in the desired area and

- ι

; a relatively small decrease in the coefficient of friction when they are wet and accordingly similar

- Have 4 borrowed dimensional and dry friction properties.

The materials of the invention are particularly suitable for use as relatively high friction pads that are in .Eingriff are with hard surfaces that move in different ways under conditions that are both dry and dry also include a wet mode of operation. The materials of the invention are e.g. in shoe soles, floor and deck surfaces, Clutch linings, pneumatic tires and solid tires and Brake pads on vehicles, such as bicycles, are suitable.

Figure 1 of the drawing shows a bicycle brake pad of the invention (10) with upper surface (16) in side view, and

Figure 2 shows the Fahrradbremskiseen of Figure 1 in the Top view. In both figures, the cushion is fastened in a conventional container (12) with a thread holder (14). The surface (16) is at an angle not more than 10 ° with respect to the

j parallels to the flat support surface in the container (12).

Figure 3 shows a top view of the pillow of the invention, interrupt the surface (16) at the grooves (20). Figures 4 and 5 give sections at 4-4 and 5-5 of the embodiment according to Figure 3 again, the pillow of the invention consists of an elastomeric mass. A cut through that Embodiments according to FIGS. 1 and 2 would look like in FIG.

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It has been found that elastomers containing a reaction product of polyepoxide and an essentially linear organic compound having a number average molecular weight (M ₁₁ ) of at least 400 and having at least two epoxy-reactive functional groups are combined with solid lubricant to form a friction material which allows a smooth, set deceleration when placed on a dry surface and maintains a relatively high deceleration when applied against a wet surface.

Polyepoxides are well known materials, for example, in the "Hanbook of Epoxy Resins" by Lee and Neville, McGraw-Hill. New York, 1967t are described in particular on pages 2 and 3 », in general, suitable polyepoxides have more than one and preferably an average of 1.5 to 2.5 oxirane groups

( - (j- ^ Q- ) per molecule and are liquid or below about 160 ⁰ O ι i

'melting solid substances. Suitable polyepoxides ^!

hear glycidyl ethers from polyols, such as butanediol, ethane

i

diol, glycerin, and polyphenols and glycidyl esters of two-j

. I.

basic acids, such as succinic acid, adipic acid, phthalic j acid and the like. They can be pure connections, are

ν
in general, however, mixtures of monomers and lower homopolymers. Mixtures of more than one polyepoxide can be used. Cycloaliphatic epoxides, such as vinylcyclohexene diepoxide, are used in the manufacture of shoe brake pads

S Ό 9 8 3 2 / D 9 7 iD

useful, but are especially useful for making softer materials, such as floor coverings. The preferred polyepoxides are glyoidyl esters and ethers, especially ethers of polyphenols, such as 2,2-bis (p-hydroxyphenyl) propane, i.e. bisphenol A. Polyphenols with nonreactive substituents phenols on the aromatic nucleus such as alkyl and halogen substituted phenols are useful, however, unsubstituted ones Polyphenols preferred. The preferred glyoidyl ethers of bisphenol A are represented by the formula

CH ₂ OH- ^ H ₂

n 0

reproduced, wherein η is 0-10 and generally 0-3. Such epoxy resins or polyepoxides become more simple and sufficient By way of the epoxy equivalent value, i.e. the number average molecular weight per oxirane group, e.g. 170 to 1590 for masses of the formula given above.

never essentially linear organic compound with at least two functional groups reactive with epoxy is an aliphatic "compound (or a mixture of compounds) with an average of more than one, generally at least 2 functional group or groups that deal with the oxirane groups of the epoxide components under hardening conditions

changes to an elastomer "or convert. Too typical Materials include low molecular weight vinyl polymers and copolymers and amino and carboxy end groups as well as oxyalkylene polymers and copolymers with amino end groups. Other suitable epoxy reactive ones functional groups include hydroxy, mercapto and carbon

. acid anhydride.

The functional groups which are capable of reacting with epoxy are preferably on a vinyl polymer backbone or polyoxyalkylene backbone terminal. The preferred polyoxyalkylene backbone consists of holds repeating Qxyalkyleneinheit, of which at least a main part consists of oxytetramethylene and at most smaller part of different repeating oxyalkylene units with 2 or 6 straight chain carbon atoms. Polyoxyalkylene residues consist of repeating oxyalkylene units with 2 to 6 straight-chain carbon atoms.

A preferred class of substantially linear organic compounds for reaction with polyepoxides consists of Amino-terminated polytetramethylene oxides such as the poly-primary amines described in U.S. Patent 3,436,359; and the poly-aek-amines described in U.S. Patent 3,580,887.

A single use all bicycle buffalo friction material suitable elastomer that is free from fillers and modification is at te In, generally has a tensile strength of

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at least about 100 kg / cm, a tear strength of at least about 20 kg / cm, an elongation of 200 ° β> or more and a hardness in the range of 45 to 85 on the Shore A scale. The elastomer is generally made by reacting a compound which contains epoxy-reactive groups, with an at least stoichiometric proportion of oxirane groups and such an additional proportion of oxirane groups as for a combination with any epoxy-reactive groups which are present in the promoter component can, is required. Accordingly, the equivalent ratio of oxirane: epoxy reactive groups can range from 1: 1 to 10: 1 and generally from 2: 1 to 8: 1. A less than stoichiometric proportion of oxirane groups results in a plasticized elastomer that is soft and weak, and ratios above 10: 1 result in products that are more plastic than elastomer. When such materials are used in brake pads, they require extremely high pressure to achieve adequate deceleration.

Allow higher molecular weight components that are reactive with epoxy and oxirane compounds with higher oxirane equivalent weights the use of higher oxirane group: epoxy reactive group ratios.

Suitable number average molecular weights (M _n ) for the epoxy reactive materials are from 400 to 200,000 and preferably from 1,000 to 100,000

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Range for vinyl polymers with a terminal carboxy 2000 to 50,000; in the case of polyoxyalkylene polymers with a terminal Primary amine (e.g. polymers containing the main proportion of repeating oxytetramethylene units) is the preferred one Range 3500 to 35000, and in the case of polyoxylalkylene polymers with a terminal secondary amine (e.g. polymers that contain repeating oxytetramethylene units as the main proportion), the preferred range is 400 to 200,000.

Known promoters for the oxirane reaction, such as tertiary amines (e.g. iris dimethylaminomethylphenol) and metal salts (e.g. tin-II-octoate), are generally used in the usual amounts. Acid promoters, such as boron trifluoride complexes, are generally to be avoided if the epoxy reactive group is basic (e.g. polyamines), but are with other reactants, such as hydroxy and carboxylic acid derivatives, suitable.

Heat modifying or reducing agents which, according to the Invention suitable are used in proportions of 10 to 60 parts or more per 100 parts of elastomer. To such Agents include solid materials that are available in an average size range of 1 to 2000 microns and are suitable as components of an elastomer formulation. Such friction reducing agents must be up to a temperature be firm by at least 150 ° ö. The presence of these materials makes the coefficient of dry friction one

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Elastomeric composition is characteristically reduced compared to the trocar coefficient of friction of the unmodified composition. The friction reducing agents also reduce the coefficient of dry friction without effectively reducing the coefficient of friction, thereby helping to achieve an appropriate balance between the wet and dry characteristics of the blastomer mass. Suitable friction modifiers for the purposes of the invention include graphite, molybdenum disulfide and _f granular polytetrafluoroethylene. Other allotropic forms of carbon are not suitable for a decrease in dry friction, although carbon black can be useful as a pigment.

In addition to the materials required above, the Mass contain additives, such as mild abrasives (such as oxides of metals such as aluminum, chromium, iron, silicon etc., with a particle size of 0.5 to 2.5 microns), reinforcing Pipes (such as cotton, nylon), fillers (such as Clay), pigments (such as carbon black) and so on. These additives are in proportions of up to 30 parts per 100 parts of elastomer, i.e. reaction product of polyepoxy and epoxy reactive material.

The compositions of the invention are made by any of the known methods, such as by mixing the components, Let the mixture stand until it has partially thickened, and then cast or injection molding, casting or compression

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sion shaping. You can then grind and compress the compression subjected or mixed and molded in an extruder. You can shed into a film or sheet shape or extruded. The molded compositions are generally thermoset to obtain the desired bonding properties to develop.

In the following examples, the components are mixed either by hand and then left to thicken (eg for one hour "at 25 ⁰ G) or, preferably combined into a cooled two-roll rubber mill with differential speed. The mixture is specified then within the specified time periods and at the! Temperatures in a printing mold. Molded into standard size bicycle brake pads which are then removed from the mold and post-cured as indicated.

Five 3 mm deep grooves with a width of about 1/2 to 1 mm, 'that are evenly spaced are in

j
the friction surface over the narrow dimension

: neither cut nor pressed in. The cushions are then placed in a conventional shoe brake ski holder and tested. According to an alternative method, the cushion using a milled mixtures are molded in a mold with hollow seams 4 for 1 to 2 minutes at 150 to 200 ⁰ G by injection molding "removed from the mold and post-cured. The post-curing can be carried out either for a few hours at 65 ⁰ G or for a few Sage, or weeks at ambient temperature.

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The tests are carried out with a commercially available (Schwinn) 5-speed bicycle with wheels with a diameter of about 66 cm, which are equipped with center-pull shoe brakes at the front and rear are carried out

The brake lever tension is adjusted so that weights of 14.5 kg for the front brake and 17.3 kg for the rear brake, work the 2.5 cm inwards from the open side of the G-handle, just allow the handles to be placed against the handlebars. Containers (4 liter kettle) with v / ater are placed over the Front and rear wheels attached, which have a pipeline provided with a valve, so that jets of water on the The rim of the wheels can be directed directly behind the brakes, so that the cushions and rims continuously during the "Wet" tests can be placed under a saucepan. The test bike with a total load of 70 kg (driver plus water tank) is on an asphalt or concrete surface at 24 km / h according to the display accelerated on the calibrated speedometer. The brakes are applied at a designated starting point a pressure between a pressure just enough to prevent the wheels from slipping and a pressure that is required to fully press the handle. The distance in which the bike is measured is measured has come to a complete standstill. When tested in wet conditions, water from the containers will continue to flow released onto the rims during the test and becomes the braking distance measured. The conditions for the "dry" test

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speak the regulations of the Consumer Product Safety Commission, 16 CFR 1512.18d (2) V and VI, published in the United S.tates
/ Federal Register on July 16, 1974 "which requires that the dry brakes stop within 4" 5 m at a speed of 15 mph when the driver weighs 68.1 kg. The specified distances are in each case the mean value of 5 tests.

! Tests show that aluminum rims and chrome-plated steel rims Comparable values result, with the exception that in each case the lüfaßbremsen Clearances for chrome-plated rims are longer. For this reason, only the values for chrome-plated rims are given in the tables.

In the examples listed in Table I, unless otherwise noted, 100 parts of epoxy reactive material of the type indicated, 40 parts of epoxy resin of the type indicated, 4 parts of tris (dimethylaminomethyl) phenol, 42 parts of a friction modifier such as is indicated (0 means that none of this has been used) and; 14 parts of metal oxide of the specified type (0 means that which nothing has been used) were mixed by hand, press-cured for one hour at 150 G ⁰ (if it is not otherwise indicated); and at 65 ⁰ C for 18 hours post-cured (in the tests 5 and 6 for 24 hours). The distances are given in meters.

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- 14 Table I.

CO I (Df

<D CO -H -P (Q

£ -1 <D ¹ OI £ j el

^) O 03 Tj: oj φ

ί> »· Η N Q ttO · Η ji | J4

MrCJr-J fi CQ d ^ I ^

Pl m U \> 3 B 9) is H αϊ Λίπ

ro + »O4> o-HN-p -ρ ο oin

0) -H -H CU P ₁ Φ · Η · Η 0) ί} J4 ^ j

1 a b 0 0 74 χ 12

2 a be d 88 x 5 12

3 e b 0 0 74 χ 16

4 ebc d 88 ^ 5 17 5 (u) f b 0 0 68 χ 19 6 (u) f b ο d 86 ^ 5 18

7 ab c (q.) 0 79 χ 9

8 abc O84 ^ 5 11

9 ab c (r) 0 90 ^ 5 12

a b g d 88 κ 5 12

abc i 90 <5 12

a b h d 83 ^ 5 12

abc j 89 ^ 5 12

a k c d 90 ^ 5 11

al c (s) d (t) 71 ^ 5 13

ame d 90 ^ 5 11

a. y ο d .73 <5 14

a. Polyoxytetramethylenediamine M ^ »11000, prepared as in Example 2 of U.S. Patent 3,824,198

b. Diglycidyl ether of bisphenol A, Bpoxy equivalent 180-200

c. "Micr of a" graphite with an average maximum

Β098 3 2 / 097Θ

Particle size of about 1 micron (Superior Graphite Co., Chicago, Illinois) '

d. Alumina powder with an average particle size from about 1 "to 1.5 microns

e. PolyCToutadiene / aorylnitrile), 20 $ acrylonitrile, with carboxy end groups, M _n «3300, B. S ¹ . Goodrich Company

f. N, N ^f -I) imethyl-polyoxytetramethylenediamine, M _n = 4700, prepared according to Example 2 of US Pat. No. 3,580,887

G. Molybdenum disulfide with an average particle size from about 5 "to 10 microns

H. Polytetrafluoroethylene powder with an average

Particle size of about 10 microns
i. Iron oxide pigment (iron-II, III-oxide), Mapico, Columbian Carton Co.

j. Chromium Oxide Pigment, JTBaker Co.
k. Triglycidyl ether of glycerine, Epon 812

1. Diglyoidyl ether of dimeric linoleic acid, Epon 871, 50 parts I.
m. diglycidyl ether of 1,4-butanediol

q .. 14 parts

ro 70 parts

p. 45 parts

t. 15 parts

u. 2 hours curing at 120 ⁰ C

x. Friction too high for controlled braking

y. 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate.

The catalyst consists of 3 parts of tris (dimethylaminomethyl) ! phenol and 3 parts of tin (II) octoate

€ 0 0 332/09 7 0

Table I shows the composition and performance of a number of bicycle shoe brake pads. Tests 1, 3 and 5 were made with materials not falling under the invention and are intended to illustrate the results obtained with the same polymer base material as in tests 2, 4 and 6 have been obtained but with no friction modifiers present, compared to the results obtained with the addition of a friction modifier, graphite, and a metal oxide, aluminum oxide, such as in tests 2, 4 and 6. In each pail this gave unmodified Polymer a brake pad which had too high a coefficient of friction, so that a controlled decrease in speed could not be achieved under dry conditions, although a suitable braking speed was achieved when The brake and rim were sprinkled with water. It can be seen that by adding graphite and alumina to the Elastomer a brake pad is obtained, which allows a set dry braking in 5 m or less and also a Permits wet braking within about 20 m or less.

Tests 7, 8 and 9 show the effect of changing graphite, content of the elastomer from the test 1. In this particular one! In this case, 10 parts of graphite per 100 parts of elastomer (14 parts

* to a total of 140 parts of epoxy reactive material

• and epoxy resin) to achieve a controlled wind speed

Inadequate decrease in capacity under dry conditions? 30 and '' 50 parts enable a controlled decrease in speed

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in dry conditions and a suitable short braking distance in wet conditions. The braking distance obtained under wet conditions is versus the amount of graphite added relatively insensitive. These tests also show that the presence of metal oxide is not required, however is beneficial in many cases. Tests 10 to 13 show the effect of various friction modifying agents, and of metal oxides in the formulation. Test 17 shows the use of a cycloaliphatic polyepoxide as the Reagent for making a shoe brake pad of the invention.

The wet braking distance is a function of the weight of the driver (or the weight of the total load). A driver performing the test with the test 2 cushion weighing 100 kg requires 16 m to come to a standstill, while a driver with a weight of 60 kg needs 10 m for this and a driver with a weight of 68 kg according to the specified tests required 12 m for this.

; Sample sets of brake pads were made as in the Test 2 having a planar friction surface, and with 2 and 5 located at equal distances grooves in the surface, wherein the: grooves sawn perpendicular to the longitudinal dimension of the surface \ found and about 3 were mm deep. All three sets of samples allow

• clear a set speed decrease under dry Conditions and allowed a stop at 5 m or less.

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When sprinkling with water, the flat cushions required 21 m, the samples with 2 grooves 16 m and the samples with 5 grooves 13 m until stop.

Except for the ear-plated values given in Tests 7, 8 and 9 Rims became the braking distance for the same cushion determined using aluminum rims. Pure all three formulations is the braking distance under dry conditions about 4 m and in wet conditions about 6 m. Ba it can be seen from this that it is much easier to brake compared to aluminum rims by two-thirds or less of the Braking distance when using chrome-plated rims below wet conditions is required and that controlled stopping under dry conditions with only 10 parts of graphite per 100 parts of elastomer is made possible.

To compare the effect of the graphite additive, other elastomer systems based on a polyester polyurethane, a polytetramethylene oxide polyurethane and polychloroprene without Friction modifier and made with about 50 parts of graphite per 100 parts of polymer. The polymers were in In each case hardened according to the recommendations of the supplier, and massive hardened masses with a Shore Α hardness of 70-90 received.

In each case, tests with brake pads on aluminum rims showed a suitable decrease in speed with a braking distance of about 5 to about 20 m under dry or wet conditions, ^. "---.

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- 19 -

The results on chrome-plated rims were unsatisfactory. When tested under dry conditions without graphite, the pads have such a high coefficient of friction that controlled braking is impossible. A controlled decrease in speed wet conditions are achieved with the urethanes, but the polychloroprene pillows show an unsuitable low Friction and poor braking. By adding 50 ropes of graphite per 100 parts of these elastomers, the Coefficient of friction modified so that adjusted braking distances under dry conditions of about 5 m with ear-plated ! can be achieved independently, but the minimum braking distances under wet conditions are more than 25 m. This clearly shows that friction reducing agents, as defined herein, only in conjunction with the class provided according to the invention of elastomers are particularly suitable

i
To explain the resistance of compositions of the invention, cushions produced according to test 2 are compared with commercial cushions of high performance (Weinmann replacement). A bicycle fitted with chrome-plated wheel rims is provided with the test 2 pads in the left front jaw and the right rear jaw. In dry conditions, the bicycle with the rider behind a cart is pulled for about 2 miles at a speed of 16-27 km / h, with the rider applying the brakes with full pressure at frequent intervals. and then relieve the pressure before sliding. At intervals of

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about 6, 15 and 16 cm, the cushions are regularly positioned changed (i.e., from right front to right back, etc.) and then the test continues. the Both of the commercially available pads lost 0.25 and 0.58 g, and the two pads of Test 2 lost only 0.05 g each.

Dr.Ve./La.

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Claims (1)

- 21 - M 3662 Pat entans prohe / 1.J Elastomeric mass with similar wet and dry friction parameters, characterized in that it consists essentially of (1) the reaction product of (a) Polyepoxide with an average of more than 1 oxirane group per molecule and a melting point below 16O ⁰ G and Cb) substantially linear epoxy reactive material with an average of more than one epoxy reactive end groups per molecule and a number average molecular weight of 400 and 200,000 and (2) Graphite, molybdenum disulfide class friction reducing agents and granular tetrafluoroethylene and (3) 0 to about 30 parts of metal oxide per 100 parts of said The reaction product consists of the polyepoxide and the linear epoxy-reactive material in proportions are, so that a ratio of oxirane to epoxy-reactive groups of 1: 1 to 10: 1 is given, and the anti-friction agent in a length of about 10 up to about 60 parts per 100 parts of said Ueai bioisj product is available. 60983 2/0970 2. Elastomeric composition according to claim. 1, characterized in that that the polyepoxide of glycidyl ether from. Bisphenol A. is. 3 «elastomeric mass according to claim 1, characterized in that that the linear epoxy reactive material contains a polyoxyalkylene backbone. 4. Elastomeric composition according to claim 3, characterized in that the polyoxyalkylene backbone has at least one main part contains repeating units made of polyoxytetramethylene. 5. Elastomeric composition according to claim 4 »characterized in that that the polyoxyalkylene backbone contains primary or secondary amino groups as end groups. 6. Elastomeric composition according to claim 1, characterized in that that the linear epoxy reactive material contains a Yinylpolymerisatebackbone. 7. Elastomeric composition according to claim 6, characterized in that the yinyl polymer backbone is butadiene-acrylonitrile and has carboxy end groups. ö. Elastomeric composition with similar wet and dry > friction characteristics, characterized in that it consists essentially of ι (1) the reaction product of polyoxytetramethylene with primary or secondary amino end groups and glycidyl ether of Bisphenol A and 009832/0970 (2) 10 to 30 (parts of alumina per 100 parts of said Reaction products and 10 to 60 parts of graphite per 100 Parts of said reaction product are divided. 9. Bicycle shoe brake pad, characterized in that that it consists essentially of an elastomeric body which has been formed from the elastomeric composition according to claim 1 and has an elongated shape with sides and ends and a bottom suitable for insertion into the shell of a Fahrradbaekenbremse is suitable, said floor one level for insertion into the shell, the elastomeric body has a flat surface opposite to the bottom and an angle not exceeding about 10 to the parallels of said Forming plane for insertion into the shell, the elastomeric body consists essentially of a friction reducing agent of the Class of graphite, molybdenum disulfide and granular polytetrafluoroethylene and the reaction product of polyepoxide and im consists of essentially linear epoxy-reactive material, said friction reducing agent in an amount of from about 10 to about 60 parts per 100 parts of said reaction product is present, the elastomeric body is also present 0 to 30 parts of metal oxide per 100 parts of said reaction product contains, the polyepoxide on average more than 1 oxirane group per molecule and a melting point below 160 0 the linear epoxy-reactive material has on average more than one epoxy-reactive end group each 609832/0970 and has a numerical average molecular weight of 400 Ms 200,000 and the polyepoxide and the linear oil material capable of reacting with lipoxy are present in proportions such that a ratio of oxirane to groups capable of reacting with hypoxy is from 1: 1 to 10: 1 . ' 1u. Bicycle shoe brake pad according to claim 9, characterized characterized in that the flat surface opposite the ground is interrupted by grooves, profiles or recesses, the polyepoxide is the glycidyl ether of bisphenol A, the epoxy reactive material is polyoxytetramethylene with primary or secondary amino end groups and the friction reducing agent Graphite is. iiroVe./La. 6 (