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Trying to get a handle on rim tire size for BFCS.?

M

Moretorque

Regular
Joined
Jun 20, 2025
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382
Location
Florida
I'm getting it all figured out for me, next move is rim tire selection. I do not want to go to a Fat tire bike but may need to. Stock the bike came with 2.1 tires and my weight( BFCS) over powered them. Then I bought Specialized 2.8 Purgatory which was by far the best for heading in the right direction of being able to push the bike. I could like run over what I wanted and the bike would just go and never give me the feeling I was gonna crash and it was like lean it over in corners and try and Super Moto it but then it would tear the valve stem out of the tubes and the tires would try and come off the rim so I think I may need a fat tire bike to do what I want to do? Then I put on Kenda El-Capo 2.4 and that does not work as well either at all. I cannot get real aggressive riding and bike will slide out from under me turning. I think I need a fat tire bike with like 4" slicks? Any input would be great. Riding an Ebike like a SM in corners would be great?
 
For the problem you are describing, I think that having the right tire for the rim is more important than having wider tires. Wider tires would, of course, give you more contact area with the pavement and a higher coefficient of friction when cornering, so less sliding out. If you are tearing the valve stem, then going tubeless would solve that problem.
 
Hey.. we already answered this in another thread....
28-40mm internal will work

..also you never stated the psi you run your tires at.. again that could be 80%+ of your problem
 
I have plenty of experience setting up high mileage riders up to and exceeding 400#. I usually recommended 48 spoke wheels and minimum 700x32 tires. Double ply and belted tires rated for touring or cargo. Microadjust seatpost. Big but not soft saddles. Large axle bottom brackets. Bigger as opposed to higher gearing.

For you in the 350# class, I would look for rims in the 25mm to 40mm inside width and 700+ grams weight range. 36 spoke and 32 spoke rims have moved on beyond anything available in 48 spoke. Gram for gram, the deeper and wider the rim the better.

On rims in that width range, I recommend 50 to 65mm touring or cargo tires because bigger tires are not built for load carrying.
 
I play around with all kinds of PSI. I am just wondering if anybody is running real big slicks on a fat tire bike and what are the results.
 
Moretorque said:
I play around with all kinds of PSI. I am just wondering if anybody is running real big slicks on a fat tire bike and what are the results.
Click to expand...
Start with the upper limit of the recommended tire pressure printed on the tire. Tread pattern doesn't matter much but casing construction is more important.
 
Apartunis said:
If you have to use 11t rear sprocket, it is not right.
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Obviously you are referring to something to do with the tire size OP is running? Not much of this thread makes sense to me?

But ignoring that, what's wrong with the 11T sprocket? Are you referring only to it in combination with the 52T ring in the post above? I'm running a Lekkie narrow/wide 36T chain ring on my MTB, stock tires on 27.5" rims, and when I drop to the 11T rear sprocket it just doesn't feel right. It feels like the drivetrain is under too much stress and I rarely use that gear. I can go nearly as fast on the 13T anyway. I ride BBS02, throttle only, no PAS.

I'm pretty anal about gearing down on slopes and will typically switch to Pas level two and pedal, gearing down until I feel no serious struggle then switch back to throttle only. I don't want the hassle of having to repair chains or replace them too often I guess ;)
 
Apartunis said:
11t sprockets murder chains fast. Murdered chains ruin cassettes, followed by chainrings. The only reason they work for pedal bike riders is because they get used less frequently and at lower intensity than more useful gears.
Click to expand...
That was sort of what I felt riding in it, I'd always be going flat out on the 13T before I dropped into it but I'll stop using it now altogether, what you say makes perfect sense. I'll adjust the rear limit screw to exclude it permanently, I need the practice with that sort of basic stuff.
 
OlderGiantFan said:
That was sort of what I felt riding in it, I'd always be going flat out on the 13T before I dropped into it but I'll stop using it now altogether, what you say makes perfect sense. I'll adjust the rear limit screw to exclude it permanently, I need the practice with that sort of basic stuff.
Click to expand...
Next time you need a cassette you can get one with a 12t or 13t top gear.
 
Oh ok, I didn't know that. I knew I could alter some. I've only ever replaced two, in my life. I guess I just retire my bikes before they get too long in the tooth, typically at about 3000 km. The one I replaced recently was on this current NRS ebike I bought used. I never inspected the cluster too close, just assumed that after 4 odd years of use the previous owner would have worn it down somewhat. When I went to buy it he told me get up it, he said it would climb trees. He was a normal bloke, an office worker type, but I know now that when you have e-power under you you can tend to get a little evil out there 😜
 
11 52 works good for me, I want to do 66 14 but that is a pain. I have to change to a wider bottom bracket.
 
OlderGiantFan said:
But ignoring that, what's wrong with the 11T sprocket?
Click to expand...
Let's talk chain wrap for example. Picture a larger cog, with the chain wrapped around it (u-shaped). Many many teeth engaged, sharing the load. Now picture the 11 tooth cog. How many teeth engaged? Five? To spread the whole load? And in practice, the derailleur almost never can fully wrap the chain so more like 3 or 4 teeth taking all the stress.
 
Given that Moretorque has a hub motor, I think it is unlikely that he is putting a lot of stress on the 11t cog at higher speeds. He switched to the 52X11 because he was spinning out completely at top speed and the motor was doing all the work. Time will tell, but hub motors don't usually wear out drive trains like mid-drives do because people aren't really pedaling that hard. Maybe if he mashes it from a stop on the 11t cog, he will do some damage, but he should be shifting to a lower gear when coming to a stop.
 
I just road a fat tire bike and the support and traction was alot better for BFCS with the big tires, The 56 T chainring is perfect, I am getting closer and closer to perfection for a COW person suffering from that syndrome...
 
Last edited:
I'm betting that bike didn't have a huge tire on a narrow rim, like the situation you still have going on.

We still don't know what PSI you use, but a larger tire is going to handle lower pressure better.
 
neptronix said:
I'm betting that bike didn't have a huge tire on a narrow rim, like the situation you still have going on.

We still don't know what PSI you use, but a larger tire is going to handle lower pressure better.
Click to expand...
I don't get this. Doesn't the tire size and use case (sand or snow) determine the best pressure to use?
 
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