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Home > Forum > Triathlon Forum > Tire wider than rim, what aero penalty?

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Tire wider than rim, what aero penalty?
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Bad Ash
Apr 30, 21 0:47
Post #1 of 6 (914 views)
Tire: 25mm Conti GP 4000 SII
Wheel: FLO 60 bought in 2015 (it has aluminum brake track rather than carbon)

By my measurements the brake track is 25mm and the tire is 28mm. It is a faff as I need to remove the wheel to get the bike in the car and that means adjusting the brakes which requires an allen (hex) key.

But anyway the query is, how much time is this costing me, if any? I have the same setup front and back, I assume the front is much more of an issue? I also assume I get less benefit of the wider tire on the front as more weight goes through the back? I'm focusing on 10 mile TTs at the moment.

EDIT: According to the FLO site the new version of this wheel (https://flocycling.com/...o-60-aluminum-carbon) has 25mm brake track and 28mm max rim width. They use the conti 25mm as the test tire in the comparisons. I measured mine further up the rim and that seems to be 28mm. So does that mean I'm OK?

EDIT to ask: are there any front wheels out there that would buy me some serious time over what I have (without breaking the bank)?
Last edited by: Bad Ash: Apr 30, 21 0:53
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Re: Tire wider than rim, what aero penalty? [Bad Ash] [ In reply to ]
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jimatbeyond
Apr 30, 21 0:52
Post #2 of 6 (908 views)
Just buy a Continental GP5000 tire that is 25mm wide and some latex tubes.
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Re: Tire wider than rim, what aero penalty? [jimatbeyond] [ In reply to ]
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Bad Ash
Apr 30, 21 0:55
Post #3 of 6 (907 views)
jimatbeyond wrote:
Just buy a Continental GP5000 tire that is 25mm wide and some latex tubes.

Does the Continental GP5000 come up smaller than the GP4000 SII?
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Re: Tire wider than rim, what aero penalty? [Bad Ash] [ In reply to ]
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MattyK
Apr 30, 21 4:10
Post #4 of 6 (825 views)
Bad Ash wrote:
jimatbeyond wrote:
Just buy a Continental GP5000 tire that is 25mm wide and some latex tubes.

Does the Continental GP5000 come up smaller than the GP4000 SII?
Yes, they are very true to size.
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Re: Tire wider than rim, what aero penalty? [Bad Ash] [ In reply to ]
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RowToTri
Apr 30, 21 5:32
Post #5 of 6 (770 views)
The size any tire will actually measure vs. the size it says on the sidewall is dependent on the internal width of the rim. I use a 23c gp5000 on a Roval clx 64 rim and it measures like 26mm while the rim outside width is 27.5 (where the brake track would be). the internal width is pretty wide at 20.9. the outside width at the widest point is 29.9.
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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
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Re: Tire wider than rim, what aero penalty? [RowToTri] [ In reply to ]
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s5100e
Apr 30, 21 6:13
Post #6 of 6 (733 views)
If I understood correctly from the Silca/ Josh info the rim width of importance is the maximum width of the rim, not the brake track width when considering aero issues and the rule of 105. In which case a tire at 28.5mm would hit the 105 rule on for that wheel max width of 29.9mm.
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