Jim’s Tech Talk
By Jim Langley
Illinois roadie Darryl wrote for help with his 2010 Cervelo RS. Here’s his question and my thoughts. Cervelos are pretty popular so if you’ve got one like Darryl’s or have some experience with the 3T fork he’s got, please share your tips to help him out.
“Hope you can help me like the many others you’ve helped in the Road Bike Rider weekly letter. My primary ride is a 58cm 2010 Cervelo RS with the OEM 3T Funda Pro fork. Until now I’ve used 25mm Panaracer Race A or Race D tires.
I learned the hard way other 25mm tires rub the top of the fork. Unfortunately it looks like the Race series was discontinued before I could stock up.
I contacted Cervelo and searched the Internet to find out which tires will fit, to no avail. Forum threads are very dated on this topic. Are you aware of a source that lists tire widths for popular tire manufacturers? (In my head I hear you saying it’s time for a new fork!)”
Nice to hear from you Darryl. Unfortunately I don’t have an answer for you and don’t know where you will find one. The only surefire way I know to determine actual tire width is to install them on your wheels, inflate them fully and then measure them with a caliper.
And, the only way I know to figure out if they will clear the sides of the fork (fork legs) and the bottom of the fork crown is to try the tires in your fork.
Because, it’s not just the fork that affects the clearance, it’s the width of the rim, too. As the rim gets narrower the tire will be taller and more likely to rub the top of the fork. With wider rims, the tire sits lower and is less likely to hit the top of the fork.
So one solution might be to try a wider front rim – though you might not want to switch your wheels or pay for a rebuild or different wheel. And, you must first make sure the wider rim won’t let the sides of the tire touch the fork legs.
You could also experiment until you are sure you’ve found a tire that fits and then stock up on them. If you buy the tires from a place that lets you return them, you’ll only end up paying for the tires that work.
I’ve been using really cheap tires because they work on my bike and solve my down tube clearance issue (keep reading). They’re inexpensive and they last a long time for me and rarely flat. Mine are Schwalbe’s Lugano 700 x 25c. I don’t know if they’ll work in your fork. I reviewed them a while back: https://www.roadbikerider.com/schwalbe-luganos-road-tires-review/.
I did a quick search to see if I could find the Panaracer tires you were using and it looks like they are still available on Amazon: https://www.amazon.com/panaracer-Race-Folding-Road-Tyre/dp/B01N5BZWUA?th=1&psc=1.
I’m sure you know that you could possibly go with a narrower tire, such as a 23 mm wide one to stop the rubbing. But, that choice will change the ride quality and flat resistance since they’re so much smaller. So you probably don’t want to take that option.
My Clearance Problem
I have 3 Cervelos and on my 2012 S5 some 25mm tires don’t hit the fork, they rub against the down tube if you can believe it. I didn’t notice it because I couldn’t hear anything. One day my friend said that it looked like the front tire was hitting the frame.
Turns out that there’s about 5 mm of clearance but anytime I hit a bump with the tires I was using at the time, the front just touched and wore right through the paint in that spot underneath the down tube (photo)! Sorry, that doesn’t help you but it shows how tight many modern bikes can be.
Going to a New Fork
Like you said, you could go with a new fork with more clearance – and maybe someone would buy your old fork on eBay to help cover the cost (it looks like new replacement carbon road forks are about $450).
If you decide to change out your fork, be sure to get a replacement that has the same geometry (offset/rake) as your original fork or else you could negatively change the handling of your bike. And, also make certain that the new fork has more tire clearance – don’t mistakenly buy one that’s just as limited as the one you have.
Readers, if any of you have tire clearance experience with a 2010 Cervelo RS with the Fundo fork, please leave a comment for Darryl with your recommendations. Thanks!
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.