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I ride a gravel bike and decided to upgrade my rear tire to a new semi-slick one so I can be a bit faster (Innova Pro Stampede -> Maxxis Receptor). The problem is though that the Maxxis Receptor has a recommended PSI range of 35 to 60 PSI while the front tire (Innova Pro Stampede) has a recommended PSI range of 50 to 75 PSI. I've heard that your front and rear tire pressures should be roughly equal with just a bit more PSI in the rear tire. I've tried using around 50-55 PSI for both of them and it feels a bit too stiff in the rear for the kind of roads I've been going through (ex. worn pavement/gravel). Any advice?

Both of the tires are 700x40c and I weigh around 63kgs/138lbs and the bike weighs around 11kgs/24lbs.

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Usually the manufacturer recommendations can be ignored. Weight on the tyre and width set the overall constraints. You then fine-tune depending on your requirements for comfort, road/trail surface and so on.

Usually a bit more of your weight will be on the rear wheel and grip on the rear wheel is less critical than on the front wheel, so people use slightly more pressure on the rear.

According to a quick internet search both of your tyres have 40mm width and are supple gravel tyres. As a 66kg person I’d use around 2.5 bar (38 PSI) when riding on gravel. Less if ridden carefully. 3.8 bar (55 PSI) would be way too much, only suitable for a much heavier person or good, new tarmac road.

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  • 50 psi in a 38mm tire is an immense amount of pressure. I would agree on ignoring the manufacturer recommendation in this case
    – Weiwen Ng
    Commented Jan 10, 2023 at 15:17
  • I see. I'll drop the rear tire pressure to around 40 PSI since I'm around 66kg but does that mean I'll also use somewhere around 35 to 40 PSI for the the front tire even though it's not in the range. (i.e. I'll ignore the recommendation for the front tire)?
    – Alex von Neumann
    Commented Jan 10, 2023 at 16:18
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    @AlexvonNeumann: Yes. Just keep in mind that low pressure increases the risk for pinch flats, so you have to be careful when riding over e.g. roots or rocks or potholes with sharp edges. I usually test tyre pressure by engaging the front brake and pressing the front wheel against a sharp object (e.g. kerb or first step of a stair) with all my body weight. If you can easily compress it all the way to the rim the pressure is probably too low. At very low pressure the tyre can “collapse” sideways in sharp turns, especially when mounted on a narrow-ish rim.
    – Michael
    Commented Jan 10, 2023 at 16:49
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    With low quality tyres or tyres with thick and stiff sidewalls low pressure can lead to cracks in the sidewall. But this shouldn’t be a problem with good gravel tyres.
    – Michael
    Commented Jan 10, 2023 at 16:51
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    FWIW, I weigh 10 lbs more than you and run 30 psi in 38 mm tires
    – Paul H
    Commented Jan 11, 2023 at 6:55
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50 PSI is usually way too much for a gravel bike. You can usually go well below the numbers stated by the manufacturer if you use a tubeless setup. It is a trial and error process and the pressure of choice will depend on the surface (e.g., the likelyhood of dangerous rocks and roots that you can hit with your rims), the way you ride and the desired ride comfort vs. speed on smooth tarmac.

However, even when going on a road ride, I do not go above 40-45 PSI with my 40 mm gravel tyres. I always ride below 40 when going offroad.

For cyclocross racing the racers would go to even values like 20 PSI but they know about every dangerous part of the track and if unpredicted stuff appears, punctures do happen even with tubulars or tubeless.

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Ignore the maximum pressure limit - it's actually what tire can stand, not you.

Correct tire pressure is mostly load and tire size related. I've experimented with tire pressures fanatically, and after all this obsession in years, I realised that every tire performs differently, in every different road condition. That's why I'm totally against having different tires front / back.

Reason is obvious. You can fine-tune each tire in lab conditions, then comes a certain road type. One is too draggy, needs more pressure, and other is too harsh for your taste. Then on mud, other tires becomes draggy, while one is too slippery for that terrain type.

If you really want to over-optimise, you'll ruin your ride. I made that mistake for too long. Tires for bikes are no big tech, but they all behave different, in different scenarios. Find the max comfortable pressure for you with trial and error, and don't bother too much. Think tires as wind: unless you ride in a velodrome, both wind and tires have very random characteristics, and they mostly slow you down.

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  • IMHO the reason why different tyres in the front and rear don’t make much sense is that when you need grip you pretty much need it for both. Sometimes people use a studded tyre in the front or a knobbier tyre in the front because a slipping front wheel is more likely to lead to a crash. But then a constantly slipping rear wheel is not much fun either, so you might as well use grippier tyres for both. The same applies when using much different pressures on the front and rear.
    – Michael
    Commented Jan 11, 2023 at 11:03
  • @Michael sure a constantly slipping rear wheel isn't much fun – but neither is a rear wheel with huge rolling resistance. The good thing with grippy-front + rolley-rear is that you avoid the worst disadvantages of each: a slippy front causes the worst crashes, and a draggy rear causes the worst power seepage. Whereas a slipping rear can usually be caught, and a dragging front can be mitigated by moving the load backwards.
    – leftaroundabout
    Commented Jan 11, 2023 at 14:20

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