dieterpi

I've been sporadically restoring a vintage peugeot bike and I'm nearly done. Now I'd like to put fatter tires on the bike, to use it on gravel roads.
Any advice on how wide can I go here?

Now I'm running 28 mm width tires on the bike. Could I run 33 or even 35 mm?



The front fork has a rubber seal, I guess I could trim the bolt to gain some height.



The tightest spot is the tire cutout in the rear. Distance cutout to cutout is about 40 mm. Putting a 35 mm tire would probably not give enough clearance I guess?

due ruote 

Ideally it’s good to have enough margin so that if a spoke breaks and your wheel goes slightly out of true, you can still ride home.

delbiker1 

Kind of hard to tell from the picture angles, but I do not see how 32 or wider are going to fit. You might have enough height on the rear brake bridge but I think not between the stays. The front tire already looks like it is about max for clearing the forks. In the end, you just have to try to see if they will fit. There is no standard on the actual size of tires, despite what the manufacturer claims the width to be.

downtube42

650b conversion? Now that 650b is marketed as 27.5, and rumours swirling that 27.5 is dead, you might find someone wanting to unload 650b/27.5 hoops.

dieterpi

I would think 32/33 mm would fit, since fitting a 32 would imply a 2 mm increase on each side. Or am I looking at it the wrong way?

Here's a better picture of the stays clearance: (don't mind the missing pedals and front derailleur )

ThermionicScott 

ryansu

I would give 32s a shot knowing that most 32s don't actually measure that wide when you put the calipers on them.Maybe some nice Panracer pasela's with the tan sidewalls for your vintage ride.

delbiker1 

Really only one way to find out. Unless you know what tires you want to use and the either the manufacturer or the seller can quote you the real measurements, not what they state them to be. Maybe a LBS can help you out with that.

nlerner

Are the tires on there now a true 28mm (i.e., have you measured)? There’s often a lot of variation between what tires are labeled and what they end up measuring, whether due to rim width, psi, or manufacturer’s variation.

Kuromori

Rule of thumb(finger) can you stick your finger in between the tire and frame comfortably? Then you have room to size up. It does look like the chainstays are going to be the tightest spot.

ryansu

You might want to replace that FD those plastic ones from the 70s are prone to cracking and it appears yours has already started on the drive side. You might need a shim for a Suntour FD but that is a popular replacement for the simplex plastic one. YMMV

Classtime 

32s are a go if you think you need that much tire for your gravel roads. 28s are pretty big already. That rubber seal thingy could be removed. It likely was there to attach the front fender.

bikemig 

As others have pointed out, there is no way to be certain without trying it out and it does look like the chain stays will be the limiting factor.

Which model Peugeot is this? It's hi tensile steel right (or carbolite or 103 or something like that)? The reason I'm asking is that some people dimple the stays to get a bit more clearance.

ThermionicScott 

You have room for at least one size bigger. Don't forget that you'd only have half of the difference on each side.

Lascauxcaveman 

Geez, you guys. 32mm easy! 35mm, maybe (probably?)

But yeah, you never know until you try. And the tighter you get in those chain stays, the more important it is to have a completely straight rear wheel.

dieterpi

Thanks for all the replies!

Now it's running specialized espoir tires. The measure exactly 28mm (I have measured ).

Panracer makes some nice looking tires. I decided on Panracer Gravelkings instead, I like the tire profile more.

It's an UO-8 type, using Carbolite 103 tubing.

Using the comments I decided on the 32 mm tires. If I would fit 35, then this would only leave me with 2.5mm clearance on each side, which would probably be to tight..

Do you mean the rubber underneath the kickstand clamp? That's just to *protect* the frame a bit.

bikemig 

That's why I asked about the model. You can run fairly massive tires on a UO 8. They came stock with 27 inch and it's no problem running 27 x 1 and 1/4 on fenders. My UE8 came stock like that.

If running 700c, you can run even wider tires, a 32c will be no problem and I'd be surprised if you can't run a 35c and quite possibly a 38c as well.

ThermionicScott 

@Classtime is referring to this doober:

HTupolev

Depends on the gravel. Well-groomed hardpack, sure. But the sky is the limit for roughness. For many the forest double-track riding out here, I'd call 28s extremely narrow; none of my friends are running anything skinnier than 35s on their allroad machines, and they're mostly going forty or bigger if clearance is adequate.

due ruote 

That’s a daruma bolt for mounting a fender.

ThermionicScott 

That is what he said, yes.

old's'cool

My experience is the sticking point on some frames with conventional (i.e. forward facing) rear dropouts, is the radial clearance between the rear tire and the chainstay bridge, when installing or removing the rear wheel. In a pinch you can gain a size or two if you are willing to partially or fully deflate the tire for R&R purposes.