Acceptable minimum tyre clearance

Hi

My Crux ‘cross bike has loads of clearance fore and sides with a 33mm tyre in there for cross racing / off road riding….but when it comes to anything in the 38-40mm range for more ‘gravel’ style riding, it becomes very tight at the sides – I’d say approx 3mm each – so what would be deemed an acceptable tolerance / width for ‘gravel’ cycling ?

Or am I just trying to convince myself that I don’t need to change the bike (as I really like it)

My old specialized was pretty tight with fatter tyres. Flex in the frame allowed a little bit of rub on bumpy terrain and it eventually wore through the chain stay on one side. You definitely want some clearance. How much will depend on frame flex and how much you like risk. I think I’d want more than 3mm on anything I was taking off road

Cross bike has different clearance to a gravel bike shocker?

Depends how much crap your tyres might pick up before they clog up, but I’d like 5mm all round personally

As above really depends on how flexy the frame is. My croix de fer is running 42mm nanos at the back and probably have about 1.5mm clearance between stays. I dished the wheel slightly towards the drive side (as the wheel tends to flex to the left due to the torque input from the drive train). I also use a bit of metal tape to prevent rubbing (mainly from mud). Works just fine, replace tape when I can remember! but is a little snugger than I would like.

Pressure is a funny thing too… If I run a tube in the nano’s I have more clearance than running tubeless. Running at higher pressures = less clearance obviously due to carcass stretch.

Personally I would be quite happy with 3mm… So long as you use some metal tape on the stays and inspect now and again

Stuff I use below:

https://www.screwfix.com/p/diall-aluminium-foil-tape-silver-45m-x-75mm/4415V?tc=WT5&ds_kid=92700058168037016&ds_rl=1249416&gclid=EAIaIQobChMI-e6FmvWS9AIVTevtCh34cQIwEAQYASABEgJ1h_D_BwE&gclsrc=aw.ds

‘sigh’ – well, if ever I asked a question i already knew the answer to, this is a case in point – but guess I was just looking confirmation from a higher source.

And I don’t fancy the metal tape route.

Thanks for the replies meantime.

British and European standards only specify a minimum of 2mm clearance between tyre and frame/fork.

So Scotroutes, by way of that, is the implication that as long as you’re within those limits, then your warranty wouldn’t be voided should you have any damage to the stays caused by using a tyre that allows you that clearance – unless they specifically state the max tyre width in the bike description ?

Moot point really if you’re not prepared to take the risk – but would be interested to know all the same

Cast your memory back to 3x chainsuck days and the damage done to ally & steel chainstays. Theres absolutely nothing that tight tyre clearance would do that’d make me worry.

Carbon different story i’d say as you dont really want to be grinding it away but i’ve had bikes where i’ve squeezed fatter than i should tyres in or mudguards with a gnats do dah clearance to tyres and run no bother.

2mm clearance will fill with mud. 3mm clearance will fill with mud. 5mm clearance will fill with mud.

As long as the wheel spins and doesnt catch under load I wouldnt worry. If there’s enough mud to stop the wheel spinning at 1mm or 5mm you’ll be walking by then.

Theres absolutely nothing that tight tyre clearance would do that’d make me worry.

Fair enough. I’d worry a little bit.

British and European standards only specify a minimum of 2mm clearance between tyre and frame/fork.

Really? I thought the ISO was 4mm either side, that’s certainly what Rourke work to (and I think Cervelo also although the key diagram seems to have disappeared from this article https://www.cervelo.com/en/further-clarity-on-tire-clearance)

OP – I ran 40mm Terrenos in a Kinesis CX frame with 44mm clearance, so 2mm either side. I could make the tyres rub if I tried hard enough (or actually, not even really that hard) and you can see the sidewall of the rear tyre definitely looks a bit scuffed. They also scored through the paint although I couldn’t tell if they were wearing through the aluminium beneath. I put some helicopter tape in there which seems to have prevented any further wear, at least, I can’t tell if the tape has been worn through or not.

Despite what many, better informed and more experienced people than I will tell you, I took extra care of the dishing of my wheel and tightened all spokes as close to design tolerance as I could and it *seemed* to improve matters.

I’d personally be happy with 3mm either side, but that’s because my frame is already damaged! If it’s a new frame (and carbon?) I’d be leary, would at least fit some sacrificial helicopter tape and monitor it to see if it is being worn through.

It’s a carbon frame – would have put Helitape on anyway prior to this post conversation – so just out of interest, I might try it just to see how it goes

PITA is that they’d thought about fork clearance- you’d get a motorcycle tyre on the front !!!

EN standards are 4mm for road and 6mm for City, MTB and e-bikes. Gravel bike with 3mm? In summer maybe and tbh I’d rather not. Dry dirt and wheel or frame flex = effective grinding wheel over time.

Cheers all – confirmed what I thought and that it’s not worth the risk….for me that is

I’ve damaged MTB frames where a slightly wonky wheel has basically caused the tyre to rub though the seat stays (GT Moto jump bike) in the space of a few days and running tyres that were a bit too fat for frames has caused them to do the same. Worsened by mud, grit, etc. and these were all relatively beefy frames compared to a carbon cross bike.

No idea If carbon is more resistant to this (assume not).