Richard5158

I need to replace a 700c x 21mm Vittoria Rally tubular tire mounted on an 18mm wide Ambrosio Montreal rim but after some searching it seems like that size is no longer available. Would it be acceptable in terms of a proper fit to replace it with a 23mm size of the same brand and model tire, or should I stick with a 21mm tire of another brand to be on the safe side?
I'd appreciate any input from anyoone with any experience with this.
Thanks,
Richard
Solvang, CA.

alo

The only time you would not want to go wider, if is there is little clearance between the tire and the frame. If there is plenty of clearance, you can go wider.

The sizes you are talking about have so little difference, it is unlikely to be an issue.

Andrew R Stewart 

I would also advice the Rally 23 tire. I have used many, maybe 10 or 15 during the years I rode sew ups. they were my daily/commuting tire. I don't think there will be any issues with your Montreal rims (which I have also used way long ago). Andy

DiabloScott

Those are some pretty narrow rims, but 23mm tires will be fine, and you'll probably like them better. No reason to use the same brand.

Richard5158

Thanks for your input. I'm pretty sure a 23mm tire will fit within the calipers and frame, I'm more concerned about the slightly wider tire fitting inside the 18mm rim and staying put after it's glued in. Based on another post it looks like it will without a problem.

Richard5158

Thanks Andy, I think that's the route I'll take, install the Rally 23's. It's on the rear wheel so it shouldn't have any negative effect on the handling with Rally 21's on the front wheel.

Richard5158

These Montreal rims are on my 81 Olmo which for me is more a show bike than a rider so I'll buy the Rally tire so it matches the one up front.
Thanks for your input.

Andrew R Stewart 

If you want to quibble the tiny crap then I could make a claim that the wider tire on the rear should be on the front. The old BMX trick. The wider tire will have greater traction and be less likely to flat. Both qualities that are more important for the front then the rear, not to mention (but I do mention...) the newer rubber will have even greater grip then old rubber does. The best- use tow 23 new tires Andy

Narhay

I have 28s on similar sized rims with no issue. You may prefer some tubular tires in a 25 size if you have the clearance.

Richard5158

It's good to know that I can mount 25 & 28mm tires on the Montreal rim. For now I'm okay going with the Rally 23mm as the bike is rarely ridden and I'm trying to keep it as period correct as possible.
Thanks everyone for the useful posts.

Andrew R Stewart 

Generally a sew up's fit to a rim is dependent on whether the rim and tire's surfaces match up in their contact, the two curves if you will. The rim's concavity of the tire seat and the tire's diameter (and sometimes if the casing stitching bulges beyond the tire's circumference). In other words when a tire in mounted on a rim does the tire's base tape contact the rim's center only (as when the rim's curve is shallow and the tire is skinny) or does the base tape contact the rim along the rim's seat sides. Ideally the tire and rim match in their shapes and the glue has max contact surface to work with. Since this aspect of rims isn't a spec published and the tire can have it's stitching bulge out If the tire is wider and thus it's contact with the rim is more along the base's sides then I see less issues then if the tire is skinnier then the rim's curve and the contact in only down the center of the base tape and rim's seat. Andy

Richard5158

Thanks Andy for the insight into the fitting of the tire into a rim. Even more reason to feel comfortable installing the 23mm Rally onto my rim.