[Scott]

I don't know if is just me, but I always seem to have a problem with tyre pressure.

Unfortunately I use my car every day for work, and end up picking up nails and other sharp material from time to time.

So far this year I have had 3 slow punctures and one leaking valve.

The problem is unless there is a dangerous dramatic blow out, (which luckily I haven't had yet), you never know until you see one of your tyre
looking a bit podgy. At this point I usually go to my local garage to pump it up only to find I have been driving on it for 2 weeks with 15 PSI in it.


I year or two ago I saw a gadget on the market that electronically monitored your tyre pressures and temperature while on the move. Limits can be set and it will alert you when pressure falls or temperature rises.
What a great idea I thought, ideal for track days. But it was 250 pounds and I went off off the idea and decided odd tyre pressures were a fact of driving.

Yesterday I was looking around the Demon Tweeks Web page and found it on special offer. And a very special offer it was, Reduced from 250 to
just 100 quid. Well this time I bought one. Its currently winging its way to me as I type.

So If you sometimes have deflation problems then this may also be a gadget for you. :smokin: :smokin:

You can find it on : www.demon-tweeks.co.uk

 

[sammy]

tyre pressure

sounds like a good idea, esp at £100 - it wasn't clear from the site whether it can be fitted retrospectively or whether you have to put it on when the tyres themselves are changed. i assume you can do it yourself when the tyres are already on.

 

[Alan]

Monitor

Sounds good Scott
Keep us posted on how easy it is to fit
ie as Sammy says does it have to be fitted when the tires are put on the rims or can it be added later ???
Best regards

 

[Scott]

Sammy/Alan,

Although I have not yet recieved it, from what I can gather from talking to the Deamon Tweek bloke, there are no wires need routing to the wheels as I'd would of thought, not even for any sort of pickup sensor. The only wire is just a battery power lead to the display unit. It picks up the signal from each corner by er....... I dun no, some sort of electronic witch craft.

The sensors can be strapped to the rims by only half removing the tyre. Simple get the local tyre shop undo one of the beads then push the tyre over to reveal the rim. I think the sensors have a counter balance weight, so to avoid having a couple of hundred grams of lead attached to the outside of the rim in order to re-balance the wheel.

I've just got a new set of rims, so will be mounting the sensor myself before I go and get the tyres fitted. Otherwise I'm not to sure how the tyre shops are going to take it having to fit this devise. But if you cross their palms with silver mine are usually very helpful.

I was thinking of mounting the display into the sun visor if I can get hold of a spare one from a car being broken.

Sounds all very simple really, but I'll let you all know. :smokin:

 

[sammy]

tyre pressure

thanks a lot for that Scott - definitely keep us posted
sammy:smokin:

 

[Scott]

NEWS UPDATE


Well,
Got the tyre pressure monitors up and running. And I must say they are really good. There was a little bit of difficulty for the tyres guy getting the 40 profile tyres over the sensors. But they went on, just took a little bit more care.

They start to work once you have reached 10mph, and then the information on the pressure and temperature starts apreaing on the screen as it picks it up. I was interested to see the temperatures varying. Although I haven't had a hack yet but just stopping from 40 at the end of my road took the cold front tyres from an ambient 24 degrees up to 26. After a 5 minute cruse at 80-90 they went up again to 32 odd.

They have already proved their worth as one of the new valves was leaking and I was able to watch it go down before getting it replaced.

Well to sum up, one very happy customer and well worth the hundred quid they cost me. Now for integrating it into a sun visor.

 

[Joss]

Hi Scott

Are there 4 sensors (1 per wheel)? and did they give a max speed rating, or is it a suck it and see situation?

Mind you, I guess you'll know if one breaks free as the reading will go all over the place

Cheers

 

[Scott]

Joss,
For some reason mine came with 6 sensors, which was meant to be 50 quid extra.

Each sensor is strapped using a 22 inch dia. jubilee clip with a counter balance weight to go the other side.

No speed rating is given, (or any warning), but ALL the tyre companys approve it. For what that is worth.

I haven't done the maths but a 50 gram sensor, + balance weight, rotating on a rim even at 180mph surely can't generate enough load to break a 12 mm jubilee clip? OR can it?

I'll get one of me egg head mates to work it out and I'll get back to you.

I could even test a clip at our lab to see where it fails and I can then comapre it to the above g load.

 

[DCD]

sounds like a cool piece of kit!:smokin: :smokin: :smokin:

Let us all know how it performs over time and if any problems arise.
Surely a gadget of the future bound to appear on new cars!!

 

[Joss]

May the Force be with you

Hmm .. well 180 mph is 80.4672 M/s

An R32 has 16" wheels with 225/50 tyres, so that's a diameter of 16"+2x(225*50%) = 0.6314m or a 1.9836m circumference

So that's 40.57 revs of the wheels per second, or 1 rev in 0.025 seconds !

A 22" circumference is 0.0889m radius.

a = 4(Pi)²r/T² = 5,775.5 m/s²

F = Ma ... so I make it 288.8 N (65 lbf) of force for 50 grammes

I hope that's right

 

[Scott]

Blimey


Joss,
First the Singers fancier then mathematician and a track day hooligan!!

Is there NO end to your talents???

Mind you we got 100 kilos @ 180mph.

And by the way, my new wheels are 17 inch NISMO's. Ow yes, Big boy now.

 

[Joss]

Renaissance man ...

Put it down to a life in computer games lot's of physics and maths in it in fact

Come on Scott, ... how did you get 100kg?

17" shouldn't make a difference as you should run lower profile tyres to compensate .. i.e. 225/45 ish

 

[Scott]

Joss,
We had a physics book out to remind me, (Well my mate), of the equations.

We also compensated for the differances in rim rotational speed and actually tread speed at 180 mph.

I must admit I did get lost be he looked and sounded confident as he worked that calculator as I have never seen before. Mine just works out my VAT, +,- and %, not too taxing.

Anyway, so I just nodded and agreed to his working out, so's not to look stupid, and hey presto 100 kg.

Easy really, but if you say 65 lb, then I'll copy down your working out go call him a thick git, and rip the piss out of him.

Ta for the ammo.

 

[Joss]

I guess he did the same

I figured the rim to be 22" circumference ... but that was 65 lbf (pound force) not just 65 lbs

I think your mate's working with kgf, so that would be 288.8 N or 29.45 kgf.

Mind you, that's only 1x50gram weight, so I guess the stress is 2x that, i.e. 58.9 kgf. and if the inside of the rim was 37" circumference, you'd get 100kg force ??

 

[Joss]

7" is more than enough

That's right Guy, but Scott said he had a 22" jubilee clip (and this is the inside of the wheel's rim).

The 100 kg f result needs a 37" circumfrence which is 11.8" diameter.

 

[Scott]

22 Inches!!!!!!!!!


You are in fact correct Guy,
Of course they are 22" Dia. Other wise 7 inch rims would be a bit small don't you think joss. Unless that is I had a 'Low Rider', with purple velvet dash, complete with tassles and hydraulic suspension. :smokin: :smokin:

Your calculations look good except for the 7 inch wheel.
But our rolling Circ. was wrong. So correcting all this we get :

70kg force

Anyone with any different? Anyone care?

 

[Joss]

Oops

I missed the "diameter" wording in Scott's first post

So what is the inside radius of your 17" rims Scott? Looking at lots of wheel pictures just now, I agree with Guy's 15" guess which gives 126 kg force .. (for 2 x 50 gram weights)

So how strong is the clip

 

[Scott]

RIGHT.


Joss,
The diameter of the rim where the sensor sits is probably 15 - 16 inches, so add the counter balance weight, 126kg sounds about right.

Well done.

Now the question is weather or not a jubilee clamp can hole 126kg or two blokes hanging from it?? Now I haven't tried it, I could test it at our lab, but I'm pretty sure it will hold that.

So I'd say that they should stay put at 180 mph. So not bad.

Now my car isn't going to be able to reach 180 mph, so thats Ok for me. BUT if any one is interested in getting them and going faster, maybe a little tug of war with a band clamp might reveal there V.Max. A bit Heath Robinson I know, but !!!

Anyway I have just had, hopefully the first and last teething problems of a low speed, (5 mph), jangleing coming from my wheels. Fearing the worst, a trip back to my local tyre shop revealed that a 120mm portion of the band clamp was loose in my wheel !!

What had happened is rather than trim all but 20 mm of excess clamp off as the book said, the bloke thought he'd be generous and leave me 120mm!! This must of stress fractured off with the compression of the tyre and road!! Thankfully the excess was long enough not to be able to get itself tangental to the rim and give me a puncture from the inside !!!

Inspection revealed that the inside of the tyre to be A.Ok.

So I'm back on the road, and monitoring my tyres as I go.