mattscq

I have this other thread already about self-built and new-bought gravel bikes but before I even get carried away with a new bike, I would love to get a sense of what I may be missing. I have been noticing on hikes lately how there are so many trails I would love to be able to ride over but my only bikes are a folding commuter and a race-forward climbing/road bike with very low tire clearance.

Has anybody had any experience with hacking a road bike into a gravel bike, if even just a temporary one? Canyon says the max tire size is 30mm but some people on other forums seem to have hacked in 34mm tires. Would I be able to get wider if I got 650b wheels? Luckily I have disc brakes so clearing calipers isn't something to worry about. Is this a terrible idea?

base2 

Going 650 is a good way to get some wider & more volumenous tires on your bike. Exactly how much, however depends on the particular bike in question. It's not hard to make an educated guess where the tire would be and measure there with a measuring tape & subtracting 8 or 10mm to ensure clearance for mud, rocks, frame flex, & tire/wheel actual size (as opposed to advertized size.)

What are you missing? I suppose it depends on what terrain you have available. If you have very few road shoulders & lots of high speed inconsiderate traffic, or super crowded MUP's, I'd say you have a lot to gain.

Gravel riding is lot like high speed hiking.

I once installed 622x41 on a vintage 700c conversion Schwinn Varsity. It worked out well. I ran it that way for a winter & treated it like a rigid mountain bike. The XTR derailleur & Jtek Shiftmate 8 with XT 11-40 cassette with custom XT 28-44 crankset would take that bike up anything.

I've also had plenty of fun on a 622x32 road bike with little more than a 11-32 cassette & 50-34 crankset. But for now my primary gravel steed is a 559x42 Rodriguez Rohloff touring bike. Really, it depends on what is appropriate for where you are riding.

I'm not really as experienced as a gravel biker as many here, but I've learned that locally (greater Seattle) we have a lot of steep terrain. 20%+ grades on fire roads are not uncommon. A 37.8% grade broke me the other day. (Holy eff...) You'll probably experience terrain rougher & steeper than any paved road you've ever encountered & get more productive fitness workouts because of it.

Others experience will vary.

My recommendation is fit what ever your bike will accept & go for a ride & make changes to equipment as you learn what you need for what/where you ride. There is so much variability, no one single recommendation can be made.

Elvo

It depends but I don't think going 650b would help if you can barely fit a 34mm. 650x47mm typically has the tire diameter of 700x28. 650x34 would be way too low.

msu2001la

It obviously depends on the terrain, but why not throw some 33c Cyclocross tires on there and find out?
Your biggest challenges will probably be the gearing and twitchy handling on downhills.

chas58

I use 32 mm gp5000 when I ride gravel and it's wonderful on the dry summer roads we have. I'm not sure 650b will work, on my Canyon the chain stays are straight and I gained no extra with by going to a smaller wheel

tangerineowl

I would tend to think if the 700c max is around a 34mm-measured slick, then even a smaller 650b like a 38mm would not fit due to fork-width clearance and chainstay width near bb.

As suggested I'd just put a 32-33mm-measured semi-slick to small knob tyre on and see how you go across those trails.

Did the same for a while on my road bike. Took it across some crazy rocky trails at times, though took it slowly through those. Good fun while it lasted.

mattscq

Reviving this, I did some more digging around and it looks like some people have managed to get 32mm tires pretty easily and possibly even 35mm with a 700c rim.

I think it may be worth a shot since tires are relatively inexpensive. Is there any caution against mounting 32 or 35 tires onto an 19mm rim? My bike came with DT Swiss P1800 splines. What advantages would I have to getting a wider rim down the road if I wanted a dedicated entry-level gravel set? Do wider rims mean even lower pressures?

chas58

you are fine. We used to mountain bike race in 19mm rims back in the day.

Try the Conti Terraspeed 35mm as I hear they run a little small (and they are fast).

canny

This sounds ominous. Did it damage your road bike?

Chi_Z

alot of carbon chainstay are hourglass shaped, you actually lose tire clearance going 650b

msu2001la

No worries about running 32-35mm tires on 19mm rims. This used to be standard for MTB and until recently it was default for cyclocross racers to run tires in this range on 19mm internal rims.

Wider rims will generally improve the handling with wider tires run at lower pressures. The tires have a lower profile when mounted on wider rims, and the sidewalls are more supported so the tire doesn't roll over as much in corners.

chas58

Good call. Apparently you are the only one on BF who has figured this out, as the popular consensus is often otherwise. You are right sir! with many carbon frames, 650 buys you nothing (or sometimes even reduced clearance if there is a dimple/crimp for 700c

mattscq

As an update: I have been running 32mm Gravelkings (the knobby ones) and it works! In fact I probably could've put 35s in. Wheels are still 700c.

chas58

you can google the ETRO tire chart, but 19mm basically fits anything below 60mm. I have some 32mms on a 12c rim.

I just got some DT Swiss G1800s (love the 24mm internal) and on it, it states the exact tire sizes and pressure range for both tubed and tubeless.
Granted, its dark grey writing on a black rim, so its not so obvious its there (look around the valve hole).

DT Swiss states a range of 30mm-69mm with a max pressure of 104-36 psi and 84-29psi for tubed and tubeless respectively.

Jrasero

As someone who owns a Canyon Ultimate CF SL Disc 8.0 I can tell you it's an amazing bike but a race bike pure and simple. Sure you can squeeze 32mm tires on the Disc Ultimate but even then that's still very road based. You are sure to find people who will believe that 28mm or above is just plain cushy and you can can tackle "light" gravel. The problem is the definition of gravel differs so greatly. Honestly the min size I would want to run is 38mm on a gravel bike with the sweet spot being 42mm. I personally like 650B wheels on gravel bikes because they allow wider tires than 700c while being very nimble.

I came to the conclusion that it's not optimal to make a race bike into a do it all bike since in the end if you want to go as fast as possible a race bike belongs only on tarmac. I ended up just bighting the bullet and found a sweet deal on a Planet X Tempest Rival 1 650B bike. The more relax geometry, racks mounts, 46mm tire clearance, flared bars, 1X setup, and titanium frame make is a great gravel bike while being able to go on long gran fondo rides while going pretty fast. Currently I am running 650B 42MM Panaracer GravelKings which are basically large slick tires, which helps with comfort, and stability while being fairly quick on tarmac albeit lacking really any tread for wet/muddy, loose, or more aggressive gravel.

MinnMan

Apparently you live in Brooklyn? How far do you have to go to find gravel? And are we talking gravel, or unpaved rail-trails?

The reason I ask is that surfaces on rail trails are seldom as challenging as actual gravel roads. For the former, a ride bike with 30 or 32 mm tires are no problem at all. for the latter, it depends a lot on the gravel. Fast hard packed gravel (what we in Minnesota tend to call "hero gravel" is a lot more forgiving than deep and very rocky gravel that you'll find in some places (such as Dirty Kanza, I'm told)

Jrasero

As someone who lives in the City as well (Bronx) it's true there aren't many mtb or serious gravel trails however running plus sized road tires or decent sized gravel tires are amazing for soaking up the crappy city streets. I personally take my gravel bike on trails in Westchester County, Dutchess County, and CT and yeah a lot of them are just hard packed gravel which you could get away with any road tire however I think the problem for me with using the Canyon Ultimate as a "gravel" bike is that it just isn't as comfortable or rugged as a dedicated gravel bike. The shorter chain stays, the lower stance, and the more aero geometry make for a great race bike but not a bike I want banging out gravel miles on. While the stock Canyon Ultimate CF SL 8.0 Disc is like 16.5lbs which is very light for a mid tier race bike, it's not something I want taking rock strikes since it's not the most robust build plus the paint for this model is uber thin.

So yeah run 30mm-32mm on the Ultimate just I wouldn't expect to do anything but very mild gravel while being a bit uncomfortable on longer or more rocky rides

babylovege

I hacked 2021 merida reacto as an cyclocross. The manufacture says the maximum clearance of this bike is 30c, but I tried schwalbe x-one 33c and it work well.
I can ride this 'aero cx' with santacruz stigmata, canyon inflite, etc. I'm satisfied with my choice.

msu2001la

I have a feeling now that road bike tire clearance has expanded upward and road discs are commonplace, we will start seeing a lot of people running road bikes with CX knobbies squeezed into them at CX races, on the amateur level anyway.

It's not optimal, but if you're just messing around doing a couple of CX races each year, and your road bike can fit 33mm CX tires, why not go for it?

enforcey

Hi there,

I actually run 35c x 700c Graveling SK's on my Ultimate for light gravel and they fit. Let me know if you want any pics.

Bildo

ANBLR@VESTAS.CO

Hey Bildo - I'm considering exactly this right now. Could you share a picture? Also, what internal rim width are you running. I'm running 17mm now but wanting to go for maybe 20mm but unsure if 35c x 700c tires will be unable to fit then...

enforcey

Sorry for the late reply. here's a pic of my Ultimate with 35c GravelKings:

piut https before this://photos.app.goo.gl/aqM5xK4G8N666gjg9

blakcloud

Pic assist

redlude97

My Oltre with knobby 32s, about 3mm clearance

Tanksalot15

Did you make any drivetrain changes? I’m wondering about whether fatter tires and more gravel climbs require changing out the rear cassette and derailleur cage. I’ve also noticed more chain slap than I’d expect on my Ultimate on rough roads - has this caused you any issues on the gravel?