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Front rims reach 170-180F on normal drive is that normal?


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I purchased a used 996 with aftermarket OZ Vella Chrome rims a few years ago and have since driven about 20,000 miles. The front rims heat up to about 170-180F after a standard drive (not using brakes). The back rims only heat up to about 120-130F. The heat does not appear to come from the brakes because the center is hotter than the caliper and rotor. I have a small vibration at highway speeds that my wife says only I notice. I replaced both front bearings right after I got the car at 40k miles and both were shot! Both wheels in the front reach approximately the same temp. When jacked up, both wheels seem to spin freely and there are not any odd noises. Is this normal?

Edited by Loren
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Makes sense. They are in the "waste" heat stream from the radiators. Touch the top of the front fenders about 2" behind the headlights after a "normal" drive especially after one with the air on. Bet they are ~170.

Edited by fpb111
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C2 or C4? Under similar condition, my rear wheels are warm to the touch and front wheels are just a little above room temp....nothing near 170F. I heard sometimes you have to remove the rotor and rotate the wheel hub by hand to feel a marginal bearing. The wheel hub is a lot lighter than the rotor + wheel so any grittiness of the bearing will be easily felt.

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170F is about 76C in new money. That's too hot to touch with comfort and almost the same temperature as your coolant under normal conditions. Have you got this right? Do you mean that your rims are too hot to touch after a run? Brake rotors can get very hot after use and cannot be touched and so can that part of the wheel near the hub where it connects on the interface. As Ahsai says, my wheels rims also get warm after a run, but 170F seems high to me. Are your tyres running below the right pressure?

After a short run of 10 miles today I tried my rims and although warm they were not uncomfortable to touch.

Edited by Hilux2400
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I have a C2

I have an infered temp gun, and we are definitely getting up to 170F. You can not keep your hand on the rims.

I am leaning toward the heat comming either from the bearings or the heat from he radiator. Since both front tires are the same temp, I think it is the radiator.

My break rotors are about 20F or more cooler than the hub area. I am running the recommended tire pressure from the manual.

When I get some time, I will take the rim off and do some more investigation.

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Definitly something is wrong and I really doubt it's from the radiator. Fresh air goes through the radiators and exits at the sides of the front bumper bottom, right ahead of the front wheels. The front wheels are seperated from the radiators by the plastic wheel liners, completely isolated from the radiators.

In fact, there are brake ducts diverting fresh air from the bottom of the front bumper to the wheel/brake/rotor to keep them cool!

Edited by Ahsai
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In that case, the only thing creating the heat would be the bearings or the brakes. The brake calipers and rotors are cooler than the hub, so it must be the bearings.

If the hub bolt is too tight, could that cause the bearings to get hot? It is just odd that both are about the same temp. I did do the work on the bearings. I did however have a local shop press in the bearings. Is it possible that incorrectly pressing in the bearings could mess them up?

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It is tough to find recommended tire temps for street tires.http://www.tune2win.com/index.php/performance_tests/tire_tech_tuning_for_your_tires/TemperaturesAll tires have a temperature range within which they will generate maximum grip. Below this point the tire will begin to slide and break away prematurely. Above this point and the tire will once again begin to slide prematurely, but can also begin to blister and suffer permanent damage. So how do you know what is too cold or too hot? Most tire manufacturers will provide a range of temperatures to target, which is a great starting point. For example, BFGoodrich recommends an operating range of 160-220F for their g-Force R1 competition tire (more on these later).Measuring tire temperatures requires the use of a pyrometer. There are two different styles available, the probe type and the infrared type. Infrared pyrometers measure the surface temperature of the tire, whereas probe type pyrometers measure the core temperature. Infrared pyrometers are great for realtime tire temperature monitoring where it is impossible to use a probe type. Because surface temperatures change very quickly, unless you are monitoring and recording the values in realtime, by the time the vehicle rolls down pit lane the surface temperatures will not be of any use. This is where the probe type pyrometer is the tool of choice, as the tire temperature is far more stable below the surface.--------------------------------------------------------------------------------http://www.bridgestonetrucktires.com/us_eng/answers/doctor_performance.aspDear Tire Doctor,What are normal surface/tread temperature ranges for truck tires after they've been running for a while?Regards, Guy^ back to top Dear Guy,Thank you for this opportunity to be of assistance.While there are many factors, such as ambient temperature, load, speed, air pressure wheel position and tire pattern that will determine the tread temperature of a truck tire in normal operating conditions, we normally experience surface tread temperatures in the range of 150 to 180 degrees Fahrenheit.Regards, Tire Doctor--------------------------------------------------------------------------------http://www.arden.org/misc/pressure.html

Edited by fpb111
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You can understand that with truck tyres temperatures might get that high as they are carrying a high load and there is quite a bit of continuous deformation at the contact point. I experience similar changes in the rear tyres of a Mercedes 4 tonne vehicle that we have. The tyres run at about 70psi, but even at that pressure there is good bit of sidewall movement which causes them to get hot after a long motorway run. This tyre temperature increases with ambient temperature, but I have never found them to be so hot that they cannot be touched.

Porsche tyres run at a lower pressure, about 45psi, with very little sidewall deflection. I would be surprised to see them reach 170F in normal use.

H

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I agree that tires can get hot depends on how you drive (e.g., sudden accelaration and deceleration) but the OP is talking about the rims and he seems to imply steady speed, light brakes kind of cruising. I doubt the tires can heat up the metal rims to 170F under that condition.

Edited by Ahsai
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Lets build a limited data base, get your pyrometers out and check temps after a 1/2 hour - 45 minute highway run, and maybe one after a run on your favorite twistys. If it stops raining here I will do one tomorrow.

Log ambient, cold pressure and hot temp.

Edited by fpb111
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I got two runs on the highway today. Rims never got above 120 deg F Tire treads did, but we are not looking at the tires.

Rim measured with a LASER equipped noncontact thermometer at the spoke lip interface. Hub at the hub wheel interface. 18" 5 spoke light weight Porsche rims. Michelin PS tires 37 psi F 44 psi R

1st run @ 69 degrees F, ambient temp according to dash gauge.

Cold start temperatures =

72 LF - 71.0 RF

71.2 LR - 71.2 RR

~20 minutes @ 75 mph - ambient 69 deg

Rim temp

112 - 119

105 - 105

Hub temp

131- 135

110 - 112

Pressures

43 - 42

50 - 50

25 min @ ~70mph - ambient temp 79 deg

Rim temp

118 - 116

105 - 107

Hub temp

134 - 137

111 - 109

Also 1 slow, ~35 - 40 mph, 30 minute run with 1 stop sign in the middle.

Rim Temp

110 - 108

101 - 101

Hub temp

116 - 120

107 - 107

Interesting note the front fenders measured ~106 deg F ~4" behind the headlights after the slow run. Top down no air on.

Edited by fpb111
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Frank, thanks for your data and taking the time to verify. It's interesting to note the fronts are always a little warmer than the rears, may be attributed to some minimal braking to stop the car before the measurements. I think your last run was closest to my DD routine and it also reflected my experience of wheels just warm but comfortable to the touch.

Edited by Ahsai
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Ahsai,

I never checked tire temps on the road and never really looked at rim temps. My rims are pretty thin with big space between the spokes. Wonder what the Twists or a denser rim would measure?

I have raced some and been an instructor for 25 years and measured many tread temps across a tire when setting up a car. Typically track tires don't really start to work until they get to ~180 deg "tread" temp and go away pretty quickly above ~240.

We need to know what pressures/tires/rims (OZ Vella Chrome rims? How thick, spokes etc) and accuracy of the measuring device OP is using. His measurements are so uniform that I suspect what he is seeing is still OK.

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Frank, yes I noticed your racing and instructor background and completely understand and agree with you on tire temp. I have same wheels as yours. I happened to pay attention to the wheel temp before because I thought I heard some front bearing noise. I checked my rims' temp like the OP but only using my bare hands. I felt all the wheels are just a little warmer than ambient so when the OP said 170F, that's clearly too hot to touch and hence my comments.

Would be curious to see what the OP finds. Maybe there's no problem like you said so he doesn't come back :)

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I went out for a drive today and made temp. readings using an inferred temp gun immediately after driving. Here is the information I got.

Outside air temp.: 85F

Drive conditions:

30 min at 75 MPH on the freeway

Exited freeway and slowed using only the engine. (One small break application from 10-0 mph)

Front wheels (both sides about the same) (36PSI)

Tire tread: 132F

Break disk: 141F

Hub: 165F (Measured where the head of the arrow is in the picture.)

Rear wheels (Both sides about the same)

Tire tread: 132F

Break disk: 115F

Hub: 109F (Measured where the head of the arrow is in the picture.)

I did some in town driving (15 min worth) after the return trip and made a few readings

Outside air temp.: 99F

Front

Tire tread: 150F

Break disk: 170F

Hub: 190-200F* (depending on the side)

*The closer I measured to the 90 deg. bend between the hub and the disk, the hotter the temp reading.

This is the hottest I have ever seen on the hub. Usually it is around 170F.

I did not measure the rear at this point.

The center of the wheel is generating a lot of heat. It is the same on both sides which leads me to believe that either something is wrong on both sides, or everything is operating normally.

post-66471-0-06385100-1370844560_thumb.j

Edited by nbeihl
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Interesting. Your 85F run, the tires were 132F. I don't think the tires heated up the rims because the rear hubs were only 109F. However, the front hubs were 165F, even hotter than the rotors at 141F. Does look like the heat source is from the hub, as opposed to be from the tires?

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As promised, here are my measurents taken by Mastercool 52224-B infrared thermometer. Left and right wheels have similar readings so I just listed front and rear. Local drive 30 min in moderate traffic.

Outside temp 72F

Front

Tread 111F

Hub 128F

Lugnut 102F

Rear

Tread 120F

Hub 115F

Lugnut 96F

Any possibility of overtightened axle nuts? Though at 350 ftlb, it's hard to imagine over tightening them...

Edited by Ahsai
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I think I misunderstood the OP original question/statement.

"The front rims heat up to about 170-180F after a standard drive (not using brakes)"

Are we looking at Rims or tires? That temp on treads is pretty much normal.

It is interesting that all of the front hubs run about 15 - 20% hotter than the rears.

Looking at our data I'm not convinced that nbeihl has a problem. His temps are higher than ours but uniform at ~20% hub/rim difference.

He might have a little more brake drag generating heat that the rotors dissipate into the hubs and under the rims.

Consider that the rotors have internal channels that pull "*cool" air into the center that is expelled as heated air out of the rotor's outer diameter against the rim inner circumference.

* Cool is relative here, 180 degree radiator exit air is cool to 3-400+ degree rotor temps after a brake application.

The hubs mostly dissipate heat through convection into the wheel and back into the rotor when it cools after braking heats things up. I wonder if the OZ rims have the same surface area in contact with the hub and convection properties to pull heat out and dissipate it as the light weight 5 spoke rims that we have do?

Nbeil it would be interesting if you could get access to a set of Porsche 5 spoke rims to do a comparison even just on the fronts.

Are you running 18" x 8" on front and 18" x 10" on rear?

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