I am getting ready for Michigan Coast 2 Coast next month and am concerned about the potential for sand. I am currently running the GravelKing SK in 35’s on a set of HED Belgium+ rims and they measure around 37. Unfortunately I don’t have much room in the back to go any wider but I have plenty of room in the front. Would there be any advantage in terms of handing, through sand in particular, if I were able to go wider up front? I know it’s fairly common in mountain biking but I’m not sure if it helps if the wider tire is in the front.
There's a case to be made for bigger tire on the front, for sure. Sand, like you describe, would be an area where a bigger tire will "float", rather than dig in. Another is when trying to improve downhill dynamics: a bigger tire on the front allows for lower tire pressure, which in turn leads to better traction, which has the benefit of causing the rear to break free before the front.
\nAn easy option would be to swap the front out for the 38 option of the same tire.
\nHave fun trying it out!
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I generally run a larger and knobbier tire in the front and a little bit faster, narrower tire in the rear. With a larger tire, I can run lower pressures for a little suspension and to get better traction through loose stuff on the descents. You also save a little bit of weight by not running the same large tire both front and rear.
I like all of these responses, and I've slowly been moving in this direction myself. Better flotation, increased traction, reduced pinch flats/bottoming out - all positives. I think the only drawback would be aerodynamics, but who cares? Coming from a road background several years ago, it was tough for me to not only lower the tires pressures substantially, but also to keep the front/rear pressures much closer to equal. I'd be running 80/90psi front/rear with 25mm tires on the road, but that was due to more weight being over the back wheel and also having zero risk of pinch flats. If I was to run 38mm front/rear on gravel, I'd keep the pressure even at maybe 35psi. But I've been experimenting with a larger 42mm front tire lately, and I've been able to drop the front down to 30psi. Seems to be working well, and I've heard that it's common to mismatch front/rear sizes and tread in the mtn bike community as well.
Thanks everyone! I'm going to go to borrow a pair of calipers from work and see how big of a tire I can fit on the front. If I'm really lucky I will be able to go with the 43, but I'm not sure that will clear my brakes. Worst case scenario the 38 should fit just fine.
JMosey wrote:Thanks everyone! I'm going to go to borrow a pair of calipers from work and see how big of a tire I can fit on the front. If I'm really lucky I will be able to go with the 43, but I'm not sure that will clear my brakes. Worst case scenario the 38 should fit just fine.
I've been doing that on my mtb for years and I like it a lot. Be careful with 38 vs 35 SK... From what I understand (and I maybe wrong), width of the new 38c is like the old 35c. I have the slick version of the 38 and they mesure less than 37 with tube on my narrowish rim (18.5 internal)...
JMosey wrote:I am getting ready for Michigan Coast 2 Coast next month and am concerned about the potential for sand. I am currently running the GravelKing SK in 35’s on a set of HED Belgium+ rims and they measure around 37. Unfortunately I don’t have much room in the back to go any wider but I have plenty of room in the front. Would there be any advantage in terms of handing, through sand in particular, if I were able to go wider up front? I know it’s fairly common in mountain biking but I’m not sure if it helps if the wider tire is in the front.
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\nI'm planning on doing this for the race, especially because if the sand on the west side. I have done 32 rear and 42 front. That is rather extreme, but allowed me to do fast road and single track.
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\nIdeally for me, i would use a 54mm 650b front and 40mm 700c rear. Either way, a large front tire will help prevent the front from sinking in sand and washing out.
clarksonxc wrote:I like all of these responses, and I've slowly been moving in this direction myself. Better flotation, increased traction, reduced pinch flats/bottoming out - all positives. I think the only drawback would be aerodynamics, but who cares? Coming from a road background several years ago, it was tough for me to not only lower the tires pressures substantially, but also to keep the front/rear pressures much closer to equal. I'd be running 80/90psi front/rear with 25mm tires on the road, but that was due to more weight being over the back wheel and also having zero risk of pinch flats. If I was to run 38mm front/rear on gravel, I'd keep the pressure even at maybe 35psi. But I've been experimenting with a larger 42mm front tire lately, and I've been able to drop the front down to 30psi. Seems to be working well, and I've heard that it's common to mismatch front/rear sizes and tread in the mtn bike community as well.
\nWhy do you not think that the same principle of less pressure up front does not apply to gravel riding? The reason for the difference is weight distribution on the bike, which applies to any bike you ride.
chunkyhugo wrote: Why do you not think that the same principle of less pressure up front does not apply to gravel riding? The reason for the difference is weight distribution on the bike, which applies to any bike you ride.
From my experience (which is limited and may not match everyone's) it comes down to the course. On a road ride, I am extremely unlikely to smash into anything large enough (rock, brach, pothold) to bottom out the rim and pinch the tire. For some of the gravel riding I do, especially in the Tug Hill region of NY, there are plenty of fast, rocky downhills with chunky rocks at the bottom. Much more likely to bottom out or pinch flat in that case if my front tire is under inflated. Believe me, I am still playing with different tire width and psi combinations, but if I'm running the same width front/rear on a rocky course, I'm going to have the same psi front/rear.
I think that chunkyhugo was trying to point out that you only need a higher PSI in the rear because your weight sits mostly on the rear tire. In the front, even with an identical tire, you would be able to run a lower PSI because there is less weight over the tire and thus less of a chance for a pinch flat. I run Hutchinson Sectors (28 mm) front and rear for winter training and run generally 3-5 PSI lower in the front for all the usual reasons (suspension, traction).
Pynchonite wrote:I think that chunkyhugo was trying to point out that you only need a higher PSI in the rear because your weight sits mostly on the rear tire. In the front, even with an identical tire, you would be able to run a lower PSI because there is less weight over the tire and thus less of a chance for a pinch flat. I run Hutchinson Sectors (28 mm) front and rear for winter training and run generally 3-5 PSI lower in the front for all the usual reasons (suspension, traction).
And I agree with that sentiment for any kind of road or nicely manicured gravel type riding. But if you're bombing down a high speed gravel descent and hit a rough patch or low water crossing, that front tire is going to be exposed to a very high impact force. If your front tire pressure is set too low, that impact force could cause the rim to bottom out on the tire.
I think that you're assuming that we/I would be running much lower in the front than the rear, where you don't really need to risk bottoming out to run simply less. The fire roads here can blow up mountain bike tires - it's mostly chunky dirt and deep sand with nice, pointy trail sharks lurking - but I still run my 33 mm Triggers with 35 PSI front, 40 PSI rear with no issues.
Pynchonite wrote:I think that you're assuming that we/I would be running much lower in the front than the rear, where you don't really need to risk bottoming out to run simply less. The fire roads here can blow up mountain bike tires - it's mostly chunky dirt and deep sand with nice, pointy trail sharks lurking - but I still run my 33 mm Triggers with 35 PSI front, 40 PSI rear with no issues.
Agreed, and no doubt tire pressure is a personal thing that's gonna change amongst riders. For instance, I know for a fact if I rode 33mm at 35psi I would end up fixing a lot of flats and getting a new set of rims at the end of the season (cause it happened!). Rider weight, finesse/style, and road conditions all play a part. That's what makes this sport so intriguing, it can be very diverse.
Agreed. I just wanted to clarify that there's nothing inherently dangerous about running lower pressure in the front tire if it's the same in the back.
