After having been pampered by the 40c tyres on my gravel bike, my Rourke road bike with 25c now seems a little harsh so I want to fit larger tyres. The current 25c (Michelin Power Endurance) blow up at about 27mm wide, with about 3mm clearance at the rear and 5mm at the front at the tightest points. If I went to the 28C version of the same tyres am I correct in assuming that it's 1.5mm added to each side and 3mm to the height?
I reckon the front will be ok but the rear will be tight on the brake pivot boss. How much clearance is normal?
I would be very careful about the front. No less than 3mm clearance just in case you pick up something that could jam in there and send you over the bars. So a 28mm tyre would probably be a bit risky. How much pressure do you run? Many roadies have them too high. If your current tyres measure up to 27mm wide you could, depending on how much you weigh, run them at around 75-80 psi on the front (less if you weigh less than 75kg) and about 85psi on the rear. At 80kg I run 23s 95/100, 25s 85/90, 28s 80/85, 32s 60/65 and 35s 40/45.
Sell the rourke. You're clearly not tough enough for a roadbike
I would be very careful about the front. No less than 3mm clearance just in case you pick up something that could jam in there and send you over the bars.
Good point that linusr, as the front clearance on my precursa is terrible, but I'd just been finding it slightly irritating with debris building up - hadn't considered the risk of catastrophic accident. Should get a smaller tyre in there.
I would be very careful about the front. No less than 3mm clearance just in case you pick up something that could jam in there and send you over the bars.
I don't think this is really a possibility is it? What are you expecting to jam in there that could possibly lock the front wheel with such force that it would flip an 80kg adult over the bars?
That said I wouldn't go any tighter than 3mm just to avoid damage to fork/tyre.
Sell the rourke. You’re clearly not tough enough for a roadbike
I was running 23c on it until a couple of years ago and never thought about the ride quality. I suspect it's a combination of the shocking deterioration of the roads and I also going soft.
@linsur 85psi front, 95psi rear and I weigh 95kg.
I think that there is enough clearance at the front to still leave 3mm all round so may change that to 28c and leave the tighter rear at 25c. I notice road buzz more at the front anyway.
For info, I had a similar question not so long ago...
Thanks @13thfloormonk, I don't think the clearance will be as tight as yours was, more like the photo near the end of the thread.
Fag paper is enough. Well I always used to be.
I wouldn't go too tight on the rear, you can get a surprising amount of flex under power IME
What are you expecting to jam in there that could possibly lock the front wheel with such force that it would flip an 80kg adult over the bars?
I've been flipped over the bars once with a jammed front wheel. Riding along a muddy track I picked up some small stones and twigs which jammed a mudguard (with no safety release) and I did a slow cartwheel. Unhurt, just embarrassing. But I'd be cautious about getting mud, twigs and gravel jammed under the fork crown. It's unlikely, but not impossible.
But I’d be cautious about getting mud, twigs and gravel jammed under the fork crown.
on a road bike?
It would obv be an absolute freak accident on the road, but then so's falling off and banging your head yet we all wear helmets. Given the consequences could be very serious, and it's a trivial fix, the risk / reward equation seems pretty clear to me.
But I’d be cautious about getting mud, twigs and gravel jammed under the fork crown.
on a road bike?
just for clarity is this for use on a british road? 🙂
like linusr I've had a front mudguard jam up but fortunately the 'safety' stays pulled out and it was a slow crash rather than a sudden flip. Granted mudguards increase the possibility of this happening but don't doubt that the mechanism for a front wheel jam is possible.
Trek state the max tyre width on their road frames and include the statement “32 c Bontrager tyres (with at least 4 mm of clearance to frame)”
I’ve been running 33mm knob lies on my road frame, not great for mud but been great for gravel. (That’s a Trek Domane)
A jam with mudguard is a different issue entirely as once the 'thing' is inside the guard there's not much chance of it escaping so it will wedge and either properly jam or attempt to destroy the guard in a bid for freedom.
With a naked bike it's really really really hard to pick up anything that would be both solid enough and sticky enough to actually jam the front wheel by the time it's come up and round, it's much more likely to hit the crown and then just bounce off, which it is free to do as there's no guard, or get smooshed and go through.
Having said all that, it's not impossible, just very very very very unlikely, and actually with less clearance then a 'thing' is less likely to jam and more likely to ping off.
This post is not advice either way though, do your own risk assessment.
I’d agree with 3 mm. I run 25c in my Propels and it is interesting to see the scratches under the front and rear (which is the tightest) arches. Those scratches only happened one way. You don’t want a jammed front wheel. Hazard and Risk.
Decent 25c tyres provide plenty of ride quality. 28c is just spoiling yourself.
