Tyre temperature difference

ZZZZ

Senior Member
Joined
Sep 19, 2014
Messages
3,671
Reaction score
1,613
Your Mercedes
.
Ignorance truly is a bliss: never before had I given a thought to the difference in tyres' temperature, between front and rear - that is, until I got myself a new gadget, in the shape of TPMS bluetooth (BLE) valves and an iPhone app.

39506866405_3ed0ee7038_o.png


Apparently (after a 15-mile trip) the driving axle is almost 10ºC hotter, which is logical, however I have no idea, whether that should only be, say a couple of degrees, or a couple of hundred :shock:

OK, so a tad exaggeration here, but still?
 

LostKiwi

Senior Member
Joined
Aug 25, 2006
Messages
31,328
Reaction score
21,575
Location
Midlands / Charente-Maritime
Your Mercedes
'93 500SL-32, '01 W210 Estate E240 (RIP), 02 R230 SL500, 04 Smart Roadster Coupe, 11 R350CDi
On an FWD car your front wheels:
Drive the car forward
Perform the bulk of the braking
Do the bulk of the cornering
Have more weight on them

The rear wheels on the other hand just have to tag along behind preventing the body scraping the tarmac.
 

rf065

Senior Member
Joined
May 30, 2007
Messages
3,520
Reaction score
998
Location
Grossbritannien
Your Mercedes
SLC300 - C250d Estate 4 Matic & Z900rs
Once when on the m/way I'd left the tyre pressures showing on the dash, I was surprised how quickly they dropped by 2 or 3 psi as soon as we hit a rain shower and the wet roads obviously cooled the tyres in only a few seconds.

Russ
 

M80

Senior Member
Joined
Jan 21, 2006
Messages
5,931
Reaction score
2,735
Location
Derbyshire
Your Mercedes
2014 639 Viano- 651, 5sp Auto. 2009 S211- 646, 5sp Auto.
I'll be interested to learn from your new gadget how much temperature difference and with it pressure difference when the sun is beating down onto one side of the car.

I noticed difference when checking pressures one summer. That might mean we make adjustments when we shouldn't as correct pressures might be restored when driving.
 
OP
Z

ZZZZ

Senior Member
Joined
Sep 19, 2014
Messages
3,671
Reaction score
1,613
Your Mercedes
.
  • Thread Starter
  • Thread starter
  • #5
I'll keep an eye on it - interesting point Martin.
I only ever adjust, or check for that matter, the pressure when the tyres are cold, of course.
Although winter 'cold' and summer 'cold' are two different things.
Here's how it looked in the morning:

40359206242_25fa321ed9_o.png


Same temp, and correct pressure difference between the front and the back.
 
OP
Z

ZZZZ

Senior Member
Joined
Sep 19, 2014
Messages
3,671
Reaction score
1,613
Your Mercedes
.
  • Thread Starter
  • Thread starter
  • #6
The rear wheels on the other hand just have to tag along behind preventing the body scraping the tarmac.

There are alternatives you know o_O :

26618969749_c5b6251b2d_o.jpg



.

.

On a serious note - thanks Alastair, I sort of know that - if only due to the fact that, I had to replace the front tyres already, and the rears are still about 6mm. The old car didn't have the S mode :) And the GLK was 4Matic :rolleyes:
 

Craiglxviii

Senior Member
Joined
Sep 6, 2015
Messages
17,781
Reaction score
7,426
Location
Cambs UK
Your Mercedes
970 Panamera Turbo; W221 S500L AMG Line, C215 CL500, W251 R350L AMG Line, plus several more now gone
On an FWD car your front wheels:
Drive the car forward
Perform the bulk of the braking
Do the bulk of the cornering
Have more weight on them

The rear wheels on the other hand just have to tag along behind preventing the body scraping the tarmac.

I’m stealing that for tomorrow’s design review!!!
 

LostKiwi

Senior Member
Joined
Aug 25, 2006
Messages
31,328
Reaction score
21,575
Location
Midlands / Charente-Maritime
Your Mercedes
'93 500SL-32, '01 W210 Estate E240 (RIP), 02 R230 SL500, 04 Smart Roadster Coupe, 11 R350CDi
There are alternatives you know o_O :

26618969749_c5b6251b2d_o.jpg



.

.

On a serious note - thanks Alastair, I sort of know that - if only due to the fact that, I had to replace the front tyres already, and the rears are still about 6mm. The old car didn't have the S mode :) And the GLK was 4Matic :rolleyes:

That's overkill.... Could have used a much skinnier one for better unsprung weight! ;)
 

LostKiwi

Senior Member
Joined
Aug 25, 2006
Messages
31,328
Reaction score
21,575
Location
Midlands / Charente-Maritime
Your Mercedes
'93 500SL-32, '01 W210 Estate E240 (RIP), 02 R230 SL500, 04 Smart Roadster Coupe, 11 R350CDi
Are you sure those cold pressures are right David? Looking at the pressure and temperature variations it suggests fronts may be underinflated.

I'd typically expect not more than 10% change cold to running.
 
OP
Z

ZZZZ

Senior Member
Joined
Sep 19, 2014
Messages
3,671
Reaction score
1,613
Your Mercedes
.
  • Thread Starter
  • Thread starter
  • #11
Are you sure those cold pressures are right David? Looking at the pressure and temperature variations it suggests fronts may be underinflated.

I'd typically expect not more than 10% change cold to running.

Well, it was really cold. I normally do 35/38 - but I'm sure you're right - I'll double check tomorrow.

Would seem to me you could use less pressure in the rear tyres and improve the ride somewhat.
I actually quite like the ride quality - it's a sports suspension, on 18" wheels (both factory) and 10mm extra width tyres (225/40).
It's not an S class by any means, but then it never meant to be.
 

oigle

Senior Member
Joined
Mar 15, 2005
Messages
3,467
Reaction score
914
Age
83
Location
Redcliffe, Queensland, Australia
Website
members.optusnet.com.au
Your Mercedes
2003 ML270 sold but not forgotten. 2022 Kia EV6 RWD LR
Are you sure those cold pressures are right David? Looking at the pressure and temperature variations it suggests fronts may be underinflated.

I'd typically expect not more than 10% change cold to running.

Particularly in English winter. Bit more pressure rise in our summers here.
 

M80

Senior Member
Joined
Jan 21, 2006
Messages
5,931
Reaction score
2,735
Location
Derbyshire
Your Mercedes
2014 639 Viano- 651, 5sp Auto. 2009 S211- 646, 5sp Auto.
I don't want to be cynical, and I can appreciate the convenience of the system,
but I would prefer to compare the display readings with results from your previous and trusted method.

Please tell, is this an Android readout on the 9" head?
 
OP
Z

ZZZZ

Senior Member
Joined
Sep 19, 2014
Messages
3,671
Reaction score
1,613
Your Mercedes
.
  • Thread Starter
  • Thread starter
  • #14
I'll do a direct comparison next time I use my Air Compressor.

The app didn't work fast enough on the 9" Android head unit, so I removed it.
Even on my iPhone it takes at least 2-3 minutes to update. The screenshots are (resized down) from iPhone.

I'd classify this TPMS as another amusement value gadget, just like the GPS/GPRS tracker, or a left mirror camera :)
 
  • Like
Reactions: M80

C350Carl

Senior Member
Joined
Feb 16, 2014
Messages
4,580
Reaction score
898
Location
Middle East
Your Mercedes
BMW 740Ld xDrive
That's pretty cool. Where did you get the valves from as I like that?
 
OP
Z

ZZZZ

Senior Member
Joined
Sep 19, 2014
Messages
3,671
Reaction score
1,613
Your Mercedes
.
  • Thread Starter
  • Thread starter
  • #16
That's pretty cool. Where did you get the valves from as I like that?
I bought them from AliExpress - just search for BLE (bluetooth low energy) TPMS VC601:

28135491219_483a76c0bf_o.jpg


Other than silly tyre icon stickers, on top of valve caps (which I removed), the finish and build quality seem very good.
 


Welwyn Merx Limited is a family run business with genuine passion, dedication and 25 years of experience dealing with Mercedes-Benz and AMG passenger cars.
Tel: 01707 395999www.welwynmerx.uk
Top Bottom