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ohanapecosh
Oct 30, 23 14:38
Post #1 of 9 (975 views)
I am pretty ignorant about bikes, so bear with me. I recently bought a Cannondale Synapse 2. My other bike is an older road bike that I'm now using exclusively for Zwift. I went back and forth about whether to buy a road bike or a gravel bike, but I do like to race (road) triathlons occasionally, and this one went on sale, so ultimately I decided on the road bike. However, I'm in the PNW, and there are a lot of gravel options out here. Therefore, I'd like to get a second set of tires. I have a couple questions:

1.) The bike comes with 30 mm tires. The spec indicates that the max allowable tire size is 32 mm: https://www.cannondale.com/...ce/synapse/synapse-2 However, eyeballing it and measuring crudely with a ruler, it's obvious there is clearance for a larger tire than 32 mm - at least 35 mm, maybe even 38 mm. Is there a concern other than clearance in terms of max tire size? Or is it OK to max out tire size as long as there is no rubbing? Is the issue possible compression / distortion of the bike when going over bumps and having interference between the wheel and the frame as a result, even if it doesn't happen nominally?

2.) How do I know the max allowable tire size the wheel (as opposed to bike frame) can support? I can't seem to find any specs for the wheel specifically. For example, if I were to buy 35 mm tires, should I expect them to fit on the same wheel, or do I need to buy a different wheel?

I'm not interested in anything serious but there are some low key gravel trails near where I live that I think would be fun to ride. I rode some gravel on my old bike with 25 mm tires and didn't particularly enjoy it, so I'm hoping it would be a bit more pleasant on 35 mm tires.
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Re: Bike questions [ohanapecosh] [ In reply to ]
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Trirunner
Oct 30, 23 16:01
Post #2 of 9 (916 views)
Hi, congratulations on your new bike!

For tire width, you only need to worry about clearance. For the front wheel, that means the tire needs to clear the front fork and for the rear wheel, it needs to clear the rear triangle: chain stays, down tube and seat stays.

Your wheels are 700, so you need to make sure that your new tire is also 700. You don't need to change the wheel, just the tire.
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Re: Bike questions [ohanapecosh] [ In reply to ]
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Twilkas
Oct 30, 23 16:47
Post #3 of 9 (878 views)
I'll leave tech issues to others, but owned a synapse and it it's a very 'do it all' kind of machine. rode plenty of 'gravel', which is to say hard packed dirt roads in the northeast. was quite capable with no special tire set up, just psi changes. for me, anyway. seemed to do everything - stiff enough to race, yet forgiving. sounds like a good choice ohanapecosh.

this review marks my experience. with tire changes, should work out fine. good luck man!
https://road.cc/...-synapse-2-rl-290441
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Re: Bike questions [Trirunner] [ In reply to ]
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fredly
Oct 30, 23 17:13
Post #4 of 9 (853 views)
Quote:
For tire width, you only need to worry about clearance. For the front wheel, that means the tire needs to clear the front fork and for the rear wheel, it needs to clear the rear triangle: chain stays, down tube and seat stays.

I think you need to define "clearance". Some of the very worst crashes I have seen occurred when small stones/sticks became wedged between fork crown/tire or chainstay bridge/BB and tire. Heck, I've had it happen to me, and I'm probably only still here to talk about it because it was the rear wheel that stopped spinning.

"If tire doesn't rub you're fine" is probably ok on a road bike, but it can be really catastrophic for someone who *knows* they're going to ride in gravel.

Published tire clearance allowances *are* there for a reason, and riding a road bike on gravel is right at the top of the list of these reasons.

For the OP - you can fudge clearance at the sides of the tire, but be really careful about clearance at the perimeter of the tire. Especially up here in the PNW... we wind up riding in a lot of conditions where stuff gets sticky and can adhere to the tire.
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Re: Bike questions [fredly] [ In reply to ]
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Trirunner
Oct 30, 23 17:56
Post #5 of 9 (825 views)
Fair points.
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Re: Bike questions [fredly] [ In reply to ]
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ohanapecosh
Oct 30, 23 21:07
Post #6 of 9 (752 views)
fredly wrote:
Quote:

For tire width, you only need to worry about clearance. For the front wheel, that means the tire needs to clear the front fork and for the rear wheel, it needs to clear the rear triangle: chain stays, down tube and seat stays.


I think you need to define "clearance". Some of the very worst crashes I have seen occurred when small stones/sticks became wedged between fork crown/tire or chainstay bridge/BB and tire. Heck, I've had it happen to me, and I'm probably only still here to talk about it because it was the rear wheel that stopped spinning.

"If tire doesn't rub you're fine" is probably ok on a road bike, but it can be really catastrophic for someone who *knows* they're going to ride in gravel.

Published tire clearance allowances *are* there for a reason, and riding a road bike on gravel is right at the top of the list of these reasons.

For the OP - you can fudge clearance at the sides of the tire, but be really careful about clearance at the perimeter of the tire. Especially up here in the PNW... we wind up riding in a lot of conditions where stuff gets sticky and can adhere to the tire.

Thank you - I really appreciate the feedback. I was hoping that gravel riding would be *less* risky than road cycling (though I intend to continue primarily doing the latter). The stuck rock / stick scenario really does not sound good. I was thinking of trying to go to 35 mm instead of the max 32 mm but maybe that extra 3 mm won't make much difference anyway. Food for thought.
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Re: Bike questions [Twilkas] [ In reply to ]
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ohanapecosh
Oct 30, 23 21:14
Post #7 of 9 (746 views)
Twilkas wrote:
I'll leave tech issues to others, but owned a synapse and it it's a very 'do it all' kind of machine. rode plenty of 'gravel', which is to say hard packed dirt roads in the northeast. was quite capable with no special tire set up, just psi changes. for me, anyway. seemed to do everything - stiff enough to race, yet forgiving. sounds like a good choice ohanapecosh.

this review marks my experience. with tire changes, should work out fine. good luck man!
https://road.cc/...-synapse-2-rl-290441

Thanks for the link! I really enjoyed reading your review.

What psi do you use for packed dirt?
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Re: Bike questions [ohanapecosh] [ In reply to ]
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mcalista
Oct 30, 23 22:31
Post #8 of 9 (707 views)
Just looked at the Cannondale website for the Synapse 2.

They specify 32mm tires with 6mm clearance on either side. The industry standard is generally 4mm clearance, so you should be able to comfortably get 36mm tires in there (although you probably want to measure clearance at the seatpost as well as the chain stays to be sure. I think part of the reason for this discrepancy is that a number of the photos feature the bike with fenders, which obviously use up some of that clearance. Fenders may be a consideration in the PNW.

The DT Swiss R470 wheels come with an internal width of 20mm, so you should be able to mount 700x36 tires on those. Although if you are going to be doing dual road/gravel use on a regular basis, a 2nd set of wheels may make easier switching than constantly remounting tires each time/
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Re: Bike questions [ohanapecosh] [ In reply to ]
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marcoviappiani
Oct 31, 23 2:04
Post #9 of 9 (638 views)
Lots of good points on this thread already, I'll just add a couple of points that I didn't see expressed.

- tire production has a tolerance, which can easily account for 2mm in difference for the same product model. Bigger tires may vary more in size.
- compatibility aside, the rim width affects the shape the tire will have once mounted (a narrower rim will force the tire into a narrower shape and viceversa).
- shape and size of knobs will affect the space the tire occupies once the tire is mounted.

That's all to say that two tires of equal width might look very different once mounted.

In your specific case you may be fine mounting 35 tires but I think you'll only know for sure once you've mounted them on the rim and put the wheel on the bike. As it's been said, you need to have enough space for little objects and mud stuck between the knobs.
A 32 gravel tire may be better for clearance peace of mind if you can find a tyre that satisfies you.
Last edited by: marcoviappiani: Oct 31, 23 2:10
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