Disc brake mounting bolts – size help? Think I ruined my forks :-(

The Ribble SLX brakes came with a 180 front mount.

If I want to use my existing discs 160 do I need another length bolts?

I didn’t realise this and I’ve just made a very costly stupid mistake!

I’m so annoyed with myself!

Don’t panic! Chances are you can use your existing 160mm setup- just remove the old caliper and the SLX will probably just bolt in teh same place.

If it doesn’t- pics!

As in I’ve just tried that and the bolts were obviously too long and have damaged the fork.

I just presumed the bolts were all one size but the Ribble ones must be longer due to the 180
Mount.

Fork lowers ruined. 🙁

Can’t see from the pics have you actually pierced the leg and you are losing oil

The bolts are all the same size whatever size rotor you run, if your running an IS fork with an IS caliper you’ll need a new mount, if you’ve got a post mount fork just take the adapter off the caliper and bolt it straight on
The only funny sized bolts I’ve seen are Avid ones with all the washers on,
The bolts that hold the adapter on will bolt it to the fork though

measure twice fit once…

That’s the thing. I took the 180mm adapter off and bolted the calliper to the fork.

The bolts must have been too long as the above happened.

Not losing oil but I imagine the strength is ruined.

got a pic of the bolts you used?

Greeble how would I measure the inside of a post mount bolt hole?

Plus I used the bolt that came with the brake.

I have had issues with bolts of different lengths being supplied with calipers and brackets. I normally spot the issue prior to getting to that stage though.

As above, if you’ve damaged the internal bore of the forks then if you use them you may damage stanchions/lose oil. If it’s just the mounts you may get away with it but you have to take a view on how much damage there is under the paint and if you trust them to stay on.

Not losing oil but I imagine the strength is ruined.

Seriously? It’s only a scratch – colour it in with permanent marker and go riding 😉

I didn’t realise because there was no force needed to screw them in. Didn’t even think to check.

The top one seems fine but the bottom one has come through, more the mount than the actual leg though.

They look like Avid tri align bolts not Shimano, the washers are deffo Avid tri align washers, if they were supplied with the brakes I’d be kicking off with where I bought em from.
The Avid system uses two sets of those washers sandwiching the adapter on each bolt which makes em short enough to be used, they’re way too long without em..

I think shimano come with those line up bolts now.

Can anyone confirm this?

why are you using avid washers?

Yup – some new shimano brakes come with those washers!

Also – they only come with one “set/pair” per bolt which when fitted go between the bolt head and the caliper body.

My new XTR ones did. First thing I did was throw them away and use the “normal” older shimano bolts I had in my spares box!

I did the same but went all the way through on a set of Manitou s once that did knacker them. If that is not the case give someone like loco a shout structure wise they may be ok if not a new set if lowers should not be to much. Them bolts are far to long though.

I think shimano come with those line up bolts now.

Can anyone confirm this?

They’re not Shimano bolts..

Greeble have I offended you in some way?

Seems you just want to wind me up?

That’s cool if that’s the case, if it’s something I did I apologise.

By the looks of it the blank end of the mounting holes isn’t structural to the mount anyway. The strength will come from the webs off the main stantion. How much force did you use to wind them through? If only a little and you didn’t have a hernia trying to winf them in, I’d just fit the calliper with the correct shorter bolt and carry on, very unlikely to have any probs.

khani – Member
They’re not Shimano bolts..

Yup – they are……

See my post above!

Silly shimano – I hated them on my avids – one of the reasons I switched!

Bolts aside – if they are M6, just run a 5.5mm drill through there CAEREFULLY to clear the back out then run an M6 tap in to clean the rest of the thread up.
If there was that little material left at the base of the hole than I wouldn’t worry about strength.
I’d clean the back with a countersink too just to make it look nice.

Forget it, as above, some black pen and ride the hell out of them 🙂

That’s the thing, I barely used any force as there was no resistance and the bolt end was miles of fitting the calliper.

They are definitely not losing oil. What length bolts would I need?

Should Ribble be supplying bolts that are clearly too long.

Greeble have I offended you in some way?

But they are Avid washers, and those bolts are far too long – how long was the allen key you used to tighten them?

Shimano 180 pM adapters come with those bolts for 180, the need to be longer as the caliper is spaced out by the adapter. 160 adaters use 2 normal bolts, 203s use 4 standard bolts.

They’re the right bolts for 1 180 adapter, not really Ribble’s fault you used them for a different setup.

No they are shimano washers and a standard Allen key. The lower mounts must be soft aluminium.

Yup – they are……

That’s weird, ive ever seen Shimano bolts like those, we’ve got three bikes at home with shimano brakes, and ive fitted a few sets for mates and they all came with shorter ones with a black washer on em, and they’re all the same size regardless of what size rotor they’re running.
Edit Aha.. That’s what they are, funny new post to post 180disc ones, two bolts instead of four, probly to save a couple of grams, that’s pretty poo…

The bolts are the correct length if if used with the 180 mount. If they were shorter and still used with a 180 mount you probably wouldn’t have sufficient thread engagement in the lowers.

If to think about it – the bolt needs to take up those washers, the mount and the caliper. If you aren’t using the mount you need shorter bolts or else the bolt bottoms out in the lowers (or cracks them – as you’ve found out – as they are cast magnesium alloy – which isn’t that strong really)

I’ve just popped to the garage and the bolts I have on my wife’s bike (160 rotor) are shorter than the ones I got with my xtr post mount for a 180 rotor

Just to get this clear I’m not blaming Ribble but to fit 160 you don’t use an adapter.

There is no mention on the as that these are 180 bolts when you buy the brakes. If have bought bolts if I’d have known.

Here – blurry pic as I was climbing over bikes to take it, but it’s a 180 Shimano mount & bolts on my bike. Bolts/Washers as supplied.

Yup – they are……

That’s weird, ive ever seen Shimano bolts like those, we’ve got three bikes at home with shimano brakes, and ive fitted a few sets for mates and they all came with shorter ones with a black washer on em, and they’re all the same size regardless of what size rotor they’re running.

I know – all of my shimano brakes (including the ones you bought!) had the same length black bolts with a captive washer only my newest XTR ones (about 2 months old) came with the hateful conical washers and longer bolts!

Mosey – it CLEARLY says “(Por le disque de 180) on there.
The issue now is not about the bolts – it’s what you want to do with the forks/lowers to sort it.
Either new lowers, new forks or the method I suggested above.

Just to get this clear I’m not blaming Ribble but to fit 160 you don’t use an adapter.
There is no mention on the as that these are 180 bolts when you buy the brakes. If have bought bolts if I’d have known.

But did you buy them as 180 with the mount fitted? In which case shimano/ribble have sent the right thing, and expected you just to bolt the mount to the forks.

It’s not quite clear-cut that you can just remove the mount and it will all fit fine – which is a bit backwards really! Unlike when it was IS to PM….

Yeah I see that but I didn’t buy 180mm adapter I bought the brakes. With every other set of shimano I bought they came with a 160mm and bolts. I just presumed these were the same bolts if you removed the 180mm adapter.

These are what I bought, it am doesn’t mention 180mm on there.

http://www.ribblecycles.co.uk/sp/mtb-bmx-bike/brakes-brakes-mtb-shimano-slx-m675-brake-levers-and-post-mount-calipers-set/shimbram313000000000

Mosey, that picture of the installation manual says it all doesn’t it? You removed the 180 mount which is effectively just a glorified spacer, and used the same bolts? The bolts are too long by the 180 mount thickness (reasoning suggests 10mm too long… the radial difference between 160 and 180).

I appreciate that, it just never crossed my mind as I’ve fitted loads of disc brakes and just removed the adapter.

The instructions don’t say anything about 160mm not can I find bolts for sale. I guess I should have asked Ribble what length bolts they are supplies with as the advert has no mention.

Perhaps if I get a 180mm disc and use the adapter the bolts will go nowhere near the damage and be fine.

These are what I bought, it am doesn’t mention 180mm on there.

Nor does it mention 160…. you removed the 180 adaptor shown in the installation manual, its common sense the bolts needed would be shorter. Just get on eBay and buy some m6 cap head screws, length 10mm shorter than the ones you’ve got. Just measure the threaded portion for length, don’t include the head.