Last year I rode a 20 MM wide rim. This year I got a good offer on a 25 MM wide rim. I think everything I read said this new “fatter” design, should be faster from an aero dynamic point of view. My question is, I will need a wider tire, so won’t that just increase rolling resistance, or am I missing something here?
Couple of other notes, both wheels are 88 MM deep, I ride them on a Shiv.
Actually you should have less RR on a wider tire.
Actually you should have less RR on a wider tire.
Thanks for the response.
Can you explain to me why? Seems like more tire on the road would create more rooling resistance. Obviously I’m wrong, since everyone is creating “fatter” profile rims, just trying to understand why that is.
Yeah, there are many articles out there that explain why, but you won’t have more RR on these rims. You’ll love them. You can also run wider tires if you want, but 23’s will work fine, too. I run 23 Michelins on a wide pair of ENVE rims and have no problems. I also have Flo 30’s with 24 & 26 (front/rear) and have no problems. Love the wider rims on hilly courses especially – descending feels a lot more controlled.
Rolling resistance is not due to friction. Rolling resistance is energy loss due to the deformation of the tire/tube. A fatter tire will deform less, therefore losing less energy. That’s also why latex tubes help with rolling resistance.
Still, 25mm seems a bit wide to me. I have some 20mm and 23mm wheelsets, and I while I do prefer the 23s, I’m not sure if the data supports them being faster overall. Other folks on the forum can give a more details answer to this, but you have to find that blend of aerodynamics, rolling resistance and comfort that works best for you.
Thanks guys for the responses very helpful.
Last question. So don’t you have to run a 25 MM tire with a 25 MM rim?
Last question. So don’t you have to run a 25 MM tire with a 25 MM rim?
No, in fact, most wide rims are probably faster with a narrower tire, like 20-23c. However, some manufacturers caution against going too narrow with tires on wide rims because you can damage the rim if you flat. Also, perhaps the tire may not seat as well? No problems with 23c on any road rim.
For example, the Zipp 303 Firecrest (a super wide rim) was more aero with a 23c tire than 25c across all yaw angles:
http://www.aeroweenie.com/assets/img/data/zipp-23-25.png
Read the article on the main Slowtwitch page about the new Ardennes Plus wheels. It goes on to talk about how the entire HED Jet line for 2014 will be 25 mm wide at the brake track and says they’ve determined the optimal tire to be a 22 mm (that’s right … 22 mm) Continental Attack. You don’t have to go with a big fat tire and, in fact, it’s not optimal.
Here’s a link to the article and, as I said, scroll down to the part where they talk about the Jet lineup for 2014.
Nope, and narrow is still faster often times.
In fact I would definitely NOT use a 25mm tire, at least on the front, for time trials/triathlons.
Thanks guys for the responses very helpful.
Last question. So don’t you have to run a 25 MM tire with a 25 MM rim?
So if I understand it right. I should get the 25 MM wheelset instead of the 20 MM wheelset. Run a 22 MM tire on the front, and either a 22 MM or a 25 MM on the back.
For a TT bike with a big guy on it. 6’7", 200 LBS. Would you ride a 88MM deep in the front and a disk or a disk cover in the back? Debatting if a 50MM would make sense up front for control.
Grand prix tires and latex tubes.
Am I missing anything?
So if I understand it right. I should get the 25 MM wheelset instead of the 20 MM wheelset.
Well, it just so happens that the latest wheels are all pretty wide. Which is good if you want to run a 23mm tire. The newer wide wheels work really well with the GP4000S 23mm clincher so that is a great way to go.
Run a 22 MM tire on the front, and either a 22 MM or a 25 MM on the back.
For a TT bike with a big guy on it. 6’7", 200 LBS. Would you ride a 88MM deep in the front and a disk or a disk cover in the back? Debatting if a 50MM would make sense up front for control.
Grand prix tires and latex tubes.
Am I missing anything?
I would run continental 4000S 23mm front and rear if it was me. It is simple and often the fastest overall option, and durable too.
Depth of front wheel just depends on your handling comfort level. Either way is fine.
I’m by no means an engineer. Just going from memory, it has something to do with the way the wider tire deflects. It makes a rounder contact patch, instead of a longer, more ovalized contact patch.
Why that helps, I can’t personally explain. Physics just says it does.
Still, for aerodynamics, a 23-ish tire will still “round out” to match the rim shape. And it’s much more like a 25 mm than a 20mm tire.
A skinnier tire will have a longer and skinnier contact patch. That means more contact with the pavement along the line representing the direction of travel. A wider tire will have a wider contact patch,but also less contact along the line representing the direction of travel.
Make any sense? I think that’s part of the rationale, anyway.
Thanks forr all the feedback
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