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Home > Forum > Triathlon Forum > Tire size for Cervelo P4/Zipp 808 front?

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Tire size for Cervelo P4/Zipp 808 front?
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automorphic
Aug 29, 17 20:16
Post #1 of 10 (1814 views)
I've got a new (for me) Cervelo P4, and my front training wheel, with a 23mm tire, has to be adjusted in the fork so as not to rub against the piece that bolts onto the form and holds the brakes. I just purchased a Zipp 808 front, and want to get a tire that's going to fit. I was thinking of going for 21mm -- does that seem like it will work, or will it give me problems in the 808 rim?

(Also, um, my training wheels might actually be cyclocross wheels. They came with the bike, and say "Fulcrum CX". Dunno if that's what's been causing my issues so far. They ride fine.)
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Re: Tire size for Cervelo P4/Zipp 808 front? [automorphic] [ In reply to ]
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grumpier.mike
Aug 29, 17 21:11
Post #2 of 10 (1795 views)
I think I know what you are talking about. So your problem is essentially a limit on tire height. Some tires are definitely taller than others, with GP4000 being the classic example. The type of 808 probably should be a consideration. The Firecrests don't have a super wide rim bed, so they will work well with a narrower tire. Firestrike and NSW are wider. The Conti SS 20 would probably be the fastest tire on a Firecrest and the GP TT, which I think is a 21 would also work well and have a little more flat protection.
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Re: Tire size for Cervelo P4/Zipp 808 front? [grumpier.mike] [ In reply to ]
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automorphic
Aug 29, 17 22:42
Post #3 of 10 (1773 views)
grumpier.mike wrote:
I think I know what you are talking about. So your problem is essentially a limit on tire height. Some tires are definitely taller than others, with GP4000 being the classic example. The type of 808 probably should be a consideration. The Firecrests don't have a super wide rim bed, so they will work well with a narrower tire. Firestrike and NSW are wider. The Conti SS 20 would probably be the fastest tire on a Firecrest and the GP TT, which I think is a 21 would also work well and have a little more flat protection.

Yeah, the tire height is the problem, exactly.

I'm not entirely sure which kind of 808 it is. It looks like this (except a front instead of a rear):

How easily do the GP TT wheels flat? I know they're not as sturdy as the GP4000s tires, which is too bad. I do Sprints/Olympics, so in a way there's less risk of a flat, but if I do flat, it's race over. I don't want that to happen.
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Re: Tire size for Cervelo P4/Zipp 808 front? [automorphic] [ In reply to ]
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nickwhite
Aug 30, 17 4:57
Post #4 of 10 (1742 views)
I'd try a GP 4000s II in size 23mm. Thousands of other people have run this setup just fine (808, P4)

20mm can be a bit tough to navigate out on the road. I love them for straight/flat TT's but personally wouldn't race a triathlon on them.
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Re: Tire size for Cervelo P4/Zipp 808 front? [nickwhite] [ In reply to ]
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moonmonkey02
Aug 30, 17 5:42
Post #5 of 10 (1729 views)
nickwhite wrote:
I'd try a GP 4000s II in size 23mm. Thousands of other people have run this setup just fine (808, P4)

I have 2011 P3C (same fork as P4) and 808 Firecrest with GP4000sII 23mm works fine.
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Re: Tire size for Cervelo P4/Zipp 808 front? [automorphic] [ In reply to ]
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grumpier.mike
Aug 30, 17 6:02
Post #6 of 10 (1721 views)
That is even the pre-Firecrest 808, which will have an even narrower rim. I would definitely go Conti TT in the 20-21 width over the GP 4000 23. The only sacrifice will be wear and maybe a tiny bit of flat resistance, but you will have better rolling resistance and almost certainly better aerodynamics. The GP 4000 -23 is a really wide tire on that rim.

On the rear, you could push the width a bit more and run the 23. The Vittoria TLR is probably the best choice.
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Re: Tire size for Cervelo P4/Zipp 808 front? [nickwhite] [ In reply to ]
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automorphic
Aug 30, 17 7:01
Post #7 of 10 (1698 views)
nickwhite wrote:
I'd try a GP 4000s II in size 23mm. Thousands of other people have run this setup just fine (808, P4)

20mm can be a bit tough to navigate out on the road. I love them for straight/flat TT's but personally wouldn't race a triathlon on them.

Which 808 is this? The one I have that is very narrow, or a more recent one?
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Re: Tire size for Cervelo P4/Zipp 808 front? [grumpier.mike] [ In reply to ]
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Scott_B
Aug 30, 17 7:04
Post #8 of 10 (1693 views)
I think the GPTT only comes in 23 and 25 widths. Once mounted, the 23 is more like a 25. I use 23 GPTTs and would love to use a 20 GPTT for the front, if only one existed. A 20 SS might be a better choice for the front, albeit with theoretically greater chance of flatting than a GPTT which in turn is theoretically more prone to flats than a GP4000.
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Re: Tire size for Cervelo P4/Zipp 808 front? [automorphic] [ In reply to ]
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nickwhite
Aug 30, 17 7:18
Post #9 of 10 (1685 views)
automorphic wrote:
nickwhite wrote:
I'd try a GP 4000s II in size 23mm. Thousands of other people have run this setup just fine (808, P4)

20mm can be a bit tough to navigate out on the road. I love them for straight/flat TT's but personally wouldn't race a triathlon on them.


Which 808 is this? The one I have that is very narrow, or a more recent one?

The 808 you have is old, like your P4. Literally thousands of people have run this exact old, narrow 808 on an old P4 with a 23mm. It'll be tight, but it is that way by design.
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Re: Tire size for Cervelo P4/Zipp 808 front? [nickwhite] [ In reply to ]
Quote | Reply
automorphic
Aug 30, 17 7:24
Post #10 of 10 (1679 views)
nickwhite wrote:
automorphic wrote:
nickwhite wrote:
I'd try a GP 4000s II in size 23mm. Thousands of other people have run this setup just fine (808, P4)

20mm can be a bit tough to navigate out on the road. I love them for straight/flat TT's but personally wouldn't race a triathlon on them.


Which 808 is this? The one I have that is very narrow, or a more recent one?

The 808 you have is old, like your P4. Literally thousands of people have run this exact old, narrow 808 on an old P4 with a 23mm. It'll be tight, but it is that way by design.

OK, I'll try the GP 4000s II. And if that somehow doesn't work or I want a change, I'll switch to the GP TT in 20-21. I'm not entirely sure why my current 23mm tire has been giving me problems, but if this setup has worked for so many others, it should work for me.

Thanks for the help guys! Slow twitch comes through once again. Now to try to find that tire for under $40...
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