How hot do shock absorbers get?

[vnx205]

I know the answer to that simple question is, "It depends".

My question really is a bit more complicated. I assume that the temperature that shock absorbers reach is influenced by the amount of energy they have dissipated in controlling the vehicle combined with the ability of the shock absorber to dissipate the heat that is generated doing that job.

I fitted a set of Bilsteins recently, so on my last trip into Bendethra Valley from the west, towards the end of the trip I tried my digital temperature sensor on the shock absorbers. That is to say, I touched the shocks with my finger.

Those of you who know the track will confirm that with the camper on the back of the Defender, the shocks had done a fair bit of work in the hour or more that the trip took.

I could keep my hand on the front ones for at least 10 seconds. The back shocks were warm enough that about 5 seconds was the limit. I am not surprised that the back ones had been working harder.

So, the questions are:
Is that a significant build up of heat or is that just beginning to get warm?
How much warmer are they likely to get with heavy, but not ridiculous use?
How hot do shocks like Bilsteins need to get before their performance deteriorates?
How hot do they need to get before they are likely to be damaged?

I am not worried that the heat I measured was critical. I'm just curious.

[justinc]

I know the answer to that simple question is, "It depends".

My question really is a bit more complicated. I assume that the temperature that shock absorbers reach is influenced by the amount of energy they have dissipated in controlling the vehicle combined with the ability of the shock absorber to dissipate the heat that is generated doing that job.

I fitted a set of Bilsteins recently, so on my last trip into Bendethra Valley from the west, towards the end of the trip I tried my digital temperature sensor on the shock absorbers. That is to say, I touched the shocks with my finger.

Those of you who know the track will confirm that with the camper on the back of the Defender, the shocks had done a fair bit of work in the hour or more that the trip took.

I could keep my hand on the front ones for at least 10 seconds. The back shocks were warm enough that about 5 seconds was the limit. I am not surprised that the back ones had been working harder.

So, the questions are:
Is that a significant build up of heat or is that just beginning to get warm?
How much warmer are they likely to get with heavy, but not ridiculous use?
How hot do shocks like Bilsteins need to get before their performance deteriorates?
How hot do they need to get before they are likely to be damaged?

I am not worried that the heat I measured was critical. I'm just curious.

Hi,

I have specific experience with Bilstein shocks in this regard, specifically rear ones as fitted to a RRC, B46-0253 part number.
During the 1992 Aust Safari we were running a 2 door RR with these shocks, single per side, and due to the wrong spring choice had the shocks build up enough heat to enable the blue rubber gaitors to melt and drip off the shockbodys like mozzarella cheese. The shocks after they cooled were still operative, hadn't leaked any gas and didn't develop any oil leaks. However, they were never after that able to cope with hard use before fading significantly, I would say they were about 50% quicker to reach their limit.

For some years after that event, the shocks were hung up on the workshop wall and were quite a conversation starter:D

I am unable to give you any scientific quantification, but by the description I hope you can get the picture:) These are great shocks.

JC

[Tombie]

IIRC Slunnie has had the paint discolour on his.

My 7100s (remote canister) get to a point that I can make spit fizzle.

[vnx205]

That information is much more useful than some sort of scientific quantification.

It is most unlikely that I will ever be in a position to put a thermometer on the shocks, but I know I could spit on them to see if they sizzled. I'm sure I would notice if the paint discoloured and I am certain I would notice the rubber gaiters melting.

So the short answer is that compared with what Bilsteins can withstand, mine were barely warm. :D I can't see me ever getting them even close to what justinc managed. :eek:

[Tote]

I have a set of Big bore monroe shocks from a Falcon ute that had got hot enough to blue the chrome finish on the rod.
Regards,
Tote

[djam1]

We use to have Unimog shocks regularly burn the paint off on dirt roads

[PhilipA]

I have seen competition Bilsteins that have blued the shaft.

My rears on my RRC discoloured the paint to a deeper yellow on the corrugations of the Kalumburu road. I touched the rears on the way to Mitchell Falls and they were very hot to touch. I couldn't leave my finger on for more than a half second without burning.
They get hotter on corrugations than anyrthing else due to the speed of movement vs dissipation of heat.
One of my fronts started to leak at the shaft but still read 95% on the Sydney Shocks Dyno before rebuild
Regards Philip A

[PhilipA]

I fitted a set of Bilsteins recently, so on my last trip into Bendethra Valley from the west, towards the end of the trip I tried my digital temperature sensor on the shock absorbers. That is to say, I touched the shocks with my finger.



On slow work like that they never get hot.
ITS THE CORRUGATIONS at speed, particularly if you try to get "onto step" at 80Kmh .
I met 2 guys at Drysdale Station who had blown the tops out of both front aftermarket shocks on their new 200 Toyos.
Regards Philip A

[Blknight.aus]

I've seen the paint burnt off, the chrome rod blues and the shock rubbers melted.

high quality shocks tend to deal with over heating lower ones... they catch fire after the inner seal fails and they "mist" their oil all over hot bits.

[justinc]

I think also I should mention that tyres play a very important part in shock absorber life/ performance, critically tyre pressures.
I had to decrease my tyre pressures once, fully loaded with trailer on I felt the Rear 'soften up' after an hour of corrugations, not particularly fast, but prolonged all the same. The DeCarbons were quite hot to the touch, and after letting the pressures down from 45 to 35psi, no more issues. (I was guilty of highway and then dirt without even thinking about dropping pressures, thought the road was a short one...:()

These same shocks are now 7 years old. No leaks, and still perform as new. I have removed them from the 110 (They were on the Rangie) and fitted standard length ones, as these were +2". I have given them to a friend of mine as they are still in excellent condition and should give years more service:)

JC

[LandyAndy]

I have a set of Big bore monroe shocks from a Falcon ute that had got hot enough to blue the chrome finish on the rod.
Regards,
Tote

Fronts????
I once had an XE Spac station wagon,worked EFI motor and later T5 box.
It constantly ruined front shocks,cheap hydraulic ones and expensive gas ones.
Loverley blue shafts every time.
Andrew

[Slunnie]

I have burnt myself on Bilsteins - they were still working better than ever at the time - knolls track in the desert, so constant full stroke action for hours with a very heavy D2 on the rear.

[rick130]

I have burnt myself on Bilsteins - they were still working better than ever at the time - knolls track in the desert, so constant full stroke action for hours with a very heavy D2 on the rear.

Ditto, and that was just a leisurely drive across Barrington Tops something like 15 years ago in SWMBO's lightly loaded (three adults and a picnic lunch) GQ Patrol.

[Dougal]

You guys should invest in an infra-red temp gun. Not the most accurate, but a lot easier on the fingers.

Anyone considered clamping aluminium heat-sinks to shock bodies?

[flagg]

You guys should invest in an infra-red temp gun. Not the most accurate, but a lot easier on the fingers.

Anyone considered clamping aluminium heat-sinks to shock bodies?

My fluke multimeter has a temp probe. its a 17b or something.. I thought it was a bit of a gimmick when I got it but its proven to be quite useful.

[rick130]

You guys should invest in an infra-red temp gun. Not the most accurate, but a lot easier on the fingers.

Anyone considered clamping aluminium heat-sinks to shock bodies?

Won't work if you have stone shields ;)

I've clamped thermocouples to a pair of Koni's but could only get the outer shell 15* above ambient in a 20km blast down a dirt road.
Unfortunately it'd been graded only a week or so before, but i did get the old girl airborne a few times :D

[Tank]

I know the answer to that simple question is, "It depends".

My question really is a bit more complicated. I assume that the temperature that shock absorbers reach is influenced by the amount of energy they have dissipated in controlling the vehicle combined with the ability of the shock absorber to dissipate the heat that is generated doing that job.

I fitted a set of Bilsteins recently, so on my last trip into Bendethra Valley from the west, towards the end of the trip I tried my digital temperature sensor on the shock absorbers. That is to say, I touched the shocks with my finger.

Those of you who know the track will confirm that with the camper on the back of the Defender, the shocks had done a fair bit of work in the hour or more that the trip took.

I could keep my hand on the front ones for at least 10 seconds. The back shocks were warm enough that about 5 seconds was the limit. I am not surprised that the back ones had been working harder.

So, the questions are:
Is that a significant build up of heat or is that just beginning to get warm?
How much warmer are they likely to get with heavy, but not ridiculous use?
How hot do shocks like Bilsteins need to get before their performance deteriorates?
How hot do they need to get before they are likely to be damaged?

I am not worried that the heat I measured was critical. I'm just curious.
Allan, first up do you have rock covers on the bottom section of the shock body, cheap insurance, secondly give Bilstien shocks Australia a call and see if they can give you some operating temps. Regards Frank.

[georgesadlik]

I measured my Fox's in the front of my D2 just from the run home from work (30+kms) on a mild day peak hour and they were at just under 90 Deg. That is way too hot to touch. So after some fast work offroad i'd expect they'd get alot hotter than that. I have read somewhere but can't confirm, that they are rated to run at temps of up to 400 Deg C. :o

Cheers

George

[vnx205]

Allan, first up do you have rock covers on the bottom section of the shock body, cheap insurance, secondly give Bilstien shocks Australia a call and see if they can give you some operating temps. Regards Frank.

I don't have the rock covers. I'll have a look at yours some time.

The problem with getting information about operating temperatures is that I would have to be able to measure the temperature on mine. I don't have a suitable temperature sensor, but I can at least spit on them and see if they sizzle. :D

[Tote]

Fronts????
I once had an XE Spac station wagon,worked EFI motor and later T5 box.
It constantly ruined front shocks,cheap hydraulic ones and expensive gas ones.
Loverley blue shafts every time.
Andrew

These ones did a lot of hard dirt miles in an XT ute with a 351. Yes they are fronts.
Regards,
Tote

[Tank]

I don't have the rock covers. I'll have a look at yours some time.

The problem with getting information about operating temperatures is that I would have to be able to measure the temperature on mine. I don't have a suitable temperature sensor, but I can at least spit on them and see if they sizzle. :D
Allan if they get hot enough to sizzle I'll bring around some steaks, the rock covers are available from most shock retailers, Regards Frank.

[Dougal]

I measured my Fox's in the front of my D2 just from the run home from work (30+kms) on a mild day peak hour and they were at just under 90 Deg. That is way too hot to touch. So after some fast work offroad i'd expect they'd get alot hotter than that. I have read somewhere but can't confirm, that they are rated to run at temps of up to 400 Deg C. :o

Cheers

George

Do you drive over plowed paddocks to get home from work?:(

[350RRC]

AFAIK Billies are monotube design and a lot of the others are twin tube, so the touch test may be objectively subjective. :)

cheers, DL

[georgesadlik]

Do you drive over plowed paddocks to get home from work?:(

Now that would be fun, but we've actually built roads over here believe it or not ? :angel:
I've got a modified shock tower so the shock is exposed to the engine heat alot more than normal. This contributes to the heat more than anything i think. They still work fine at this temp. Not sure how the closed foam shocks like tough dog would respond to this sort of heat though.

Cheers

George.