Yamaha TRX850 Enthusiasts Forum

looking at replacing all my front/rear brake discs bolts and all caliper bolts as there looking - well crap really

any suggestions other than Probolt as i think these are great but expensive and i know i wont be able to contain myself - £££$$$$$$ and my wife WILL slap me

I used stainless mushroom headed allen bolts for the discs, if I do them again I'll use ones with the biggest hex I can find, and a harder grade of steel (if they are available). My replacements had a smaller hex than the std bolts and a couple rounded off as I torqued them up.

Not much help I guess... lol..

G

stops me buying the same as you did though and possibly wasting £50

probolts are nice just expensive

you can get 8mm button head stainless bolts from any engineering supplies and you will pay about £5 for the lot ,,but if youve got a r1wheel they have a shoulder on the shaft and are about £3 each

IMO stainless is too soft for anything needing more than a modicum of torque.

If it were me, I would buy oe bolts for the discs and calipers.

You could try nylon if you feel adventurous?!?

http://cgi.ebay.co.uk/yamaha-fzr-rd-xj- ... dZViewItem

Stainless bolts should be the same strength or stronger than oem.

cheers for that philk

stainless stronger? not neccessarily. stainless is soft. threads gall easier. heads chew easier. stainless is just that - it isn't particularly hard.

martin young wrote:stainless stronger? not neccessarily. stainless is soft. threads gall easier. heads chew easier. stainless is just that - it isn't particularly hard.

Agreed, but what i was saying was Stainless bolts should be the same strength or stronger than oem.

As the oem disk bolts are very soft.

FYI most Stainless disk bolts are A4 316 spec,

8.8 Steel Tensile Strength 800N/mm Yield Strength 640N/mm
10.9 Steel Tensile Strength1040N/mm Yield Strength 940N/mm
12.9 Alloy Steel Tensile Strength1220N/mm Yield Strength 1100N/mm
A2-70 302 Stainless Tensile Strength700N/mm Yield Strength 450N/mm
A4-80 316 Stainless Tensile Strength800N/mm Yield Strength 600N/mm

In racing circles they do not recommend using stainless....
of course im happy to be corrected

bolts of differing materials can be procured in a variety of tensile strengths. I am sure that with research stronger bolts in other materials could be found.

the tensile strength will not stop the socket of a stainless mushroom head bolt chewing up when being torqued up. generally stainless mushroom head bolts have insufficient meat on them to accept the torque needed for mounting brake discs. However, as the bolts should be replaced with the discs it may be ok to use them, although I would not.

Bolts tighten due, in part, to deformation of the thread. Stainless is soft and will deform too much if loosened and tightened a number of times - such as caliper bolts which should be getting took out regularly to clean and grease brakes, hence I would not use them on that application either. this is why stainless is not often used in racing applications.

OE bolts have (hopefully) been enginered for the application they are used on. As I feel brakes are a critical application, I would stick with OE bolts.

As would I. And if you want to save weight and money only use three per side in a triangular pattern! Don't laugh, we always did that with the TZs and FZR400s back in the day.

I do not endorse this for regular everyday (low maintenance) riding though...

vote +1 to what ppl said.

DONT USE stainless on disks. Stainless has too much malleability.. Means it deforms easy. IE: think of a spring. Use OEM... you will probably find they are 8.8 anyway, but still.. dont skimp out on breaks !!

bring back drums i say...