MegaSack DRAW - This year's winner is user - rgwb
We will be in touch
I have a 2016 (maybe 2017) GT Grade gravel bike. I'd like to make it a bit more winter off-road friendly so thinking of some wider and more knobbier tyres to handle a bit more mud / looser dirt conditions. Also some more gravel orientated wheels for a bit more strength, the current wheels are roady wheels.
Currently the bike has some 32c Clement semi slick tyres on which are very good in the summer but terrible in current conditions. With a bit of experimenting (ie packing out the current tyres to make them bigger) I think I can increase tyre size to 35-37mm; 40mm just very finely brushes the chain stays so with a bit clearance 37 is probably about max, 35 to be on safer side?
I've also been reading it's possible to use 650b wheels in a 700c frame to try and squeeze in some higher volume tyres into older frames designed for much narrower tyres (like mine). So I got a cheap pair of Hunt 650b Gravel wheels in the black Friday sale a while back.
I finally got round to offering the new wheels up to the bike to see what size tyres I could fit. Turns out I can only fit a 40mm tyre in there 42mm just about touches the sides so with a bit of clearance I think 40mm is max. The chain stay design stays quite parallel around tyre rim and only starts to diverge and taper out later on. Front fork is better and looks like I can go 40+ on the front but rear chain stays are the limiting factor.
So now left wondering if the bike's geometry is going to be wrong as I can't get the volume into the 650b tyres to bring them more inline with skinny 700c tyres?
Wondering if I should send the wheels back and get a 700c gravel set and accept 35mm is the max?
Or will the current wheels be OK just not a massive difference? I do need some stronger gravel wheels and these were cheap so I can live with them just as long as they don't ruin the bike.
I ran 26 inch wheels in a 27.5 frame- fine.
My wife's bike is for 29 wheels, but has a 26 in the back to slacken the head angle and lower thr bottom bracket. She didn't notice any difference after I swapped the wheel but I noticed she was less worried riding downhill.
I'd suggest it will be fine based on loads of gravel frames taking 700 or 650b. And the fatter tires will be different.
If you want better in the mud what about some cyclo cross mud tires?
I have both sets for my mason bokeh. I actually prefer the 650b with 47mm over the 700c with 40mm. It rides more like a mountain bike. So I’d go with the 650bs.
It sounds as if the problem for the OP, if I'm understanding the post correctly, is that they can only fit 650x40, which is quite narrow (my Trig is meant to be able to take 700x40 or 650x2.1").
I'm not sure where the pinch point is or whether they could fit 700cc with something approaching 40mm.
I tried the same in several bikes and had the same issue. Biggest tyre I could fit cost me a lot of ground clearance as well. Gave up and found that 35mm is plenty in the back for nearly everything.
2016/17 was really before gravel became such a big thing and lots of bikes/frames were really designed around 32 or 35mm tyres (CX rule limitations). It's not surprising that 40mm, or thereabouts, is the maximum you can fit. Bigger knobbles will eat into your max tyre width, as will clearance for any mud or crap that sticks to the tyres.
I wouldn't be too worried about geometry changes. I rode my Amazon with 700x40 and 650x47 tyres on and off for a few years and it didn't have a noticeable effect on handling.
Sorry just read back my post it’s a bit long winded.
TLDR: I can currently fit 700c-35 tyres or 650b-40 tyres on my bike
Will the bike still handle ok with the smaller wheels with only +5 in extra width / volume?
From what I gather normally when you swap 700c to 650b you want a significant volume increase eg something around 10mm.
The pinch point is width between the chain stays. The frame design keeps them quite straight rather tapering out. So dropping a wheel size doesn’t give me much more room for ac wider tyre.
I like Scott routes i swap between 700c 40mm and 650b 47mm. But in a few odd situations the slightly lower bottom bracket is a pain. Obviously 40mm would be tougher
A mate runs wtb resolutes on 650b. I think they 42mm on the side wall. Not sure 0f the actual size. But they seem to do everything just fine. Might be worth researching them
I don't think it'll be worth it for 5mm extra width. The smaller wheel/tyre combo will hook up more in rougher conditions - boulders/tree roots etc. so you need to factor trail conditions into the equation too. The reason I flipped between 700x40 and 650x47 was exactly that - I'd decide based upon my route choice.
I've been riding reasonably hard this winter in some pretty crazy muddy conditions, albeit not a lot of big descents or long climbs, more just linking up lots of muddy dog walking trails in forests and along riverbanks.
700x40 has been fine, you're not going fast enough (or I'm not anyway) to need the suspension effect of wider tyres, and I firmly believe that narrower tyres 'cut through' more, am amazed where I can find traction.
Best investment is foam inserts to protect tyre and rim at lower pressures. If I'd bought these first I might even have stuck with 700x35 and enjoyed the extra tyre clearance...
Thanks folks for the feedback so far ... Sounds like 600x40 isn't going to make a massive difference over 700X35.
Next dilemma I have ...
Current set of 700c wheels are some mid level roady wheels I don't know if they'll cope with a gravel usage?
The 650b wheel set I have bought are gravel wheels so a bit heavier and a bit stronger. Stick with these or send them back and get a set of 700c gravel wheels?
The tracks around me are woodland trails, not rocky but will have lots of roots.