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Old 10-18-08, 02:03 PM   #1
kmart
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Mavic MA40 max pressure?

I just got hold of some killer tires that are 145 max psi. What's the highest *pressure I can go on my MA40 rims (these are the ones that came on my '86/'87 Centurion Dave Scott Ironman)? The wheels are wheelsmith with serial #105250, if that's any help.

EDIT: for coherency.

Last edited by kmart; 10-18-08 at 03:06 PM.
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Old 10-18-08, 04:01 PM   #2
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Nobody knows, the max PSI of these rims...
Nobody knows, but Jesus....
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Old 10-18-08, 04:38 PM   #3
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How much do you weigh? For your average person, there is absolutely no need or advantage to inflating any tire to 145 psi. Have you ever seen a car manufacturer recommend that tires get inflated to their maximum allowable pressure? Do car manufacturers recommend different pressures for different tires? for different rims?
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Old 10-18-08, 05:34 PM   #4
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Well, the max I will inflate 700x23s to is 120 if I'm trying to go fast or 110 if I want to take it easy. Basically I just want to know if they can handle 120 psi. I'm 150lbs.
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Old 10-18-08, 11:37 PM   #5
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Quote:
Originally Posted by kmart View Post
Well, the max I will inflate 700x23s to is 120 if I'm trying to go fast or 110 if I want to take it easy. Basically I just want to know if they can handle 120 psi. I'm 150lbs.
Firstly, at 150 lbs, you will not be able to tell the difference between 110 and 120 psi. Secondly, how are you measuring the pressure? Few gauges are accurate enough to measure the difference between the two. Thirdly, few pumps that indicate pressure over 100 psi are actually even capable of achieving these pressures on a reliable basis. I generally recommend the thumb hard rule: if you can depress the tire with your thumb add a bit more air. The stronger you are, generally the heavier and stronger rider you are: hence better return on harder tires. The weaker you are, generally the slower you are and less punishing you are on the tires.

As for the pressure limits of the MA40, you are perfectly safe at 120 psi.
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Old 10-19-08, 01:32 AM   #6
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Maybe you can't feel the difference but I think I can, even at my puny weight. It's not a night and day difference, obviously. I calibrated my pump using an electronic pressure gauge and it tends to be accurate within +/-5 psi. It's just a department store pump with a plastic gauge on it and it's been working fine for years.

I realize there is a point of diminishing returns and experimentally I would put it at 120psi. Depending on the tire and on the road (and the rider, and wind, etc...), 10psi fewer DOES make a difference.
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Old 10-19-08, 01:37 AM   #7
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You have to be able to measure the tire deflection when the bike is loaded... over inflating your tires will have a negative effect on handling and impart a very harsh ride which will slow you down.

At 142 pounds I do not run any of my high psi tyres at their maximum as I find it decreases the performance of the bike.

With that being said I do run a MA40 front and am building up a matching rear for my fixed gear and feel confident that they could handle 120 plus psi with no issues even though I will probably be running them at 100-110 psi to adjust for my weight.
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Old 10-19-08, 01:18 PM   #8
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Years a go when I had MA40s, I routinely ran some continental 700x20 tires at 140psi. No problems ever experienced. Perhaps it's the knowledge that I knew they were pumped that high, but I felt like there was difference between 140 and 120 The bike seemed faster at the higher pressure. It also seemed like I could feel every pebble in the road.
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Old 10-19-08, 01:23 PM   #9
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Unless you are riding on ultra smooth surfaces, 120psi and over is too high. You end up with so little rubber touching the road you can lose traction. Traction is important to me during descents where my life is on the line. It's important on climbs on less than perfect pavement.

Just because the tires claim they can go to 145psi is no reason to pump them up that high.
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