Wheel Weight/Pressure Limits - Am I Being Stupid?

Or alternatively - am I being unreasonable?

I’m shopping for training wheels. Nothing fancy, just a solid set with a decent rim width (for 30mm tyres), adequate spokes and suitable hubs for year round big miles on the road. I’m not a lightweight rider and I live in the UK.

I’m chatting with a manufacturer after their wheels piqued my interest. Looks like they fit the bill, including being designed with extra strength/spokes for an increased weight limit.

However, with a 30mm tyre (measured, not claimed) you cannot pass 70psi on these wheels. That makes no sense to me. If a rider was on the weight limit for the wheels both the Silca and Sram calculators would put you at 80+psi - that’s 14% over max for the rim and would void the warranty.

To get the Silca calculator below the pressure limit you’d have to be 50kg under the manufacturer’s stated weight limit! Doesn’t this mean these rims aren’t suitable for heavy riders, if used with 30mm tyres?

(The Silca calculator has always worked well for me. I’ve tried going harder and softer. Going softer I have bottomed out the rim before and the cornering deteriorates, so I generally stick to their suggestions pretty closely)

Mind giving your weight?

Are these ‘hookless’ rims?

3 Likes

Sounds about right to me.

I ride Scribe wheels with 30mm tubeless tyres. At 80kg and my bike at 10kg with 21mm inners heres what i use.

Even if i weighed 100kg my rear would be 70psi.

I’m 85kg (90kg at most, 84kg at race weight - I’m tall), bike is 10kg, kit, food, water, spares is c.5kg - so normal unloaded training rides would be up to 105kg. I also use the bike for loaded commuting, so add another c.5kg for bag, laptop, shoes, clothes, towel, lights etc taking me up to 110kg at the top end.

Wheels are apparently made for 130kg, so I’m well under the weight limit

No, I’ve got no interest in hookless for the road

At 85kg…

Which wheels are you talking about?

Yeah, but I’m at 105-110kg system weight and these are 20mm internal.

Sram: 70.1 / 74.6
Silca: 72 / 73.5

If you’re planning on running a 30mm tire I’m pretty sure hookless is going to be more secure, more aero, and a better all around decision. Not an expert but based on my understanding hookless suits your scenario much better

2 Likes

Except for the max pressure for hookless. I wouldn’t be able to run anything under 31mm and be within max pressure specs. I’m planning to run a 30mm, but I might run a 28, or a 32, or something else at some point.

The question I’m asking is whether it’s reasonable to advertise a wheel with what seems to me to be a contradiction between the weight limit and the pressure limit?

It’s pretty normal. It’s manufacturer suggestions. CX tubeless tires seem to always recommend 35-50/60psi. They’re typically run at 20-30psi

If you warranty something, no one is going to ask for a pic of you on a scale or anything.

1 Like

The wheel manufacture has no clue what tire you will be installing. They can offer a weight limit for their component, they can’t offer a weight limit for a wheel/tire system. If your selected tire puts you over their max pressure, then maybe you should look at a wider tire to be able to run a lower pressure?

2 Likes

running below the minimum is different than running over the max.

I disagree. The problems that arise from too high a pressure are different than too low of pressure, but going outside manufacturers recommendations on either side has risks.

Hmm, I’m not sure thats true. Enve has a good article

and some info in this Roval tubeless done right

Worth giving those a read if you are interested in tubeless for road. FWIW my engineer brain is sold on hooked rims for road tubeless, for the additional safety, ability to run higher pressures, and no limitations on tire choices.

I’m currently running 30c S-Works RapidAir tubeless at 80-85psi and these are very comfortable on rough roads, as comfortable as some 32c at 65psi that I’ve run on wider rims.

@BigRed if you want to run higher pressures and not be limited by tire choice, you are going to need to go with hooked rims like these Roval Rapide II that I’m running:

1 Like

:exploding_head:
With the specs I have put into the Silca calculator, you have to be in excess of a combined 123kg before they recommend going above 70psi slightly with a standard tube (if its a p’ture resistant tubeless youd get upto 141kg). You are no where near that @BigRed so no need to worry IMO.


High performance tubeless according to the silca calculator will see you exceed 70psi at just 90kg (combined) but my guess is that this would be super light/ soft rubber with no integrity that would transfer pressure straight to the rim and you’d be unlikely to be commuting on it, as it would probably p’ture every 5mins on our cr@p roads. (Unhelpfully the Silca link to explain tyre type and why it makes such a difference is down).

If they’re not hookless I’m struggling to see where the 70psi limit is coming from as that’s normally a hookless thing. What wheels are you looking at?

2 Likes

It comes out at 72 / 73.5 for me. I find the descriptions in the drop downs not particularly helpful - what really are “mid range” or “high performance” tyres, similarly, why isn’t average speed just a number? Anyway, I’ll be using something like a GP5000 S TR or I might try out the Vittoria Corsa N.ext and my average ride speeds are commuting = 30-32kph, long steady rides = 30-36, shorter/sharper training rides or chainy = 33-43.

Clearly there isn’t one exact pressure that should be used for everything, it’s just a guide. But then also, as Silca point out from their testing, even brand new pumps can be 7-8psi out, so I won’t be buying wheels where the recommended Silca/Sram tyre pressure is close or exceeds the maximum rim pressure, just like I wouldn’t buy a wheel if I’m over the specified weight limit.

My advice for people running tubeless road tires on hookless rims:

  1. Use enough pressure to avoid bottoming out, as this can up a tear in your sidewall. This goes double for rear tires.

  2. Check your pressure before you ride in case you have lost pressure. Especially if it’s cold overnight or you just installed the tire.

  3. Cary spare tubes, levers, and a mini pump (plus co2 if you choose, not as a replacement for a mini pump), in cases you get a leak. Anything bigger that a pinhole will not seal permanently with sealant alone, especially if it’s not fresh aggressive race sealant (the kind you have to pour in). You will eventually need to put a tube in the tire. Carrying a Shrader adapter is also a good idea, since you can fill up at gas stations.

  4. Repair holes that sealant won’t fix with regular patches and cement… which is most of them.

  5. Get a compressor and a presta valve filler for installs. Buy sealant in big bottles… You will be pulling and installing a lot of tires. If you have a hard time getting the beads up, pull the valve cores and use an inflator that will work without it.

  6. Don’t buy the thinnest tires. I had zero issues with GP5000 TLs but S-Works Turbo 2Bliss have been a nightmare as rear tires.