TGS tyre specs: Manual vs Auto

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Philip Chidlow
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TGS tyre specs: Manual vs Auto

Post by Philip Chidlow » Tue Mar 20, 2007 11:17 am

I have a question: Why, in the original specification were 165/70 R14s OK for the manual 16TGS but the automatic version is listed as being shod with 155R14 (80s)? The 155R14 80s on my 16TGS auto are noisy Nankangs and I want Michelins/Klebers and they don't do them in that size anymore.

Could I fit 165/70 R14s OK? I can get those for £38 a corner fitted, all in.
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Post by Kitch » Tue Mar 20, 2007 11:43 am

Can't see why they'd make a difference TBH....unless its to do with rolling resistance? Can't see how they'd be all that different though.

I know my old 16TRS auto had 175's on it and was fine.

It might be because the auto's were proving thirsty as far as fuel consumpsion figures go, so they tried to fit tyres with less rolling resistance to bring it up a bit?

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Post by Philip Chidlow » Tue Mar 20, 2007 11:56 am

Kitch wrote: It might be because the auto's were proving thirsty as far as fuel consumpsion figures go, so they tried to fit tyres with less rolling resistance to bring it up a bit?
Well, it might work (although I imagine the difference between 155 Nankang Tractor Tread specials and Micheilin 165's would be negligible I'd have thought!).

I got 35-36mpg from the 16TGS auto on a 119 mile trip on Saturday. Not too bad I thought seeing as most was at 70-80 mph or accelerating to get there...
• COMING SOON... 1992 Citroen BX TZD Turbo Hurricane
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Post by Kitch » Tue Mar 20, 2007 12:05 pm

Thats brilliant economy.....every 16 I've owned or known someone who's owned it has proved thirsty....even more so than the 19's. The auto I had took the piss....20mpg if you're lucky. I thought it was a fault, but the engine was sweet as a nut, had just passed an MOT and the carb wasn't, even a year old.

Maybe it was the tyres? :lol:

tim leech

Post by tim leech » Tue Mar 20, 2007 12:49 pm

Ive always wondered that myself Phil, 155 section tyres on a car of that size are daft! You could eaily fit 175/65/14s with no worries.

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Post by jeremy » Tue Mar 20, 2007 2:21 pm

At the end of the 'Struts' section of the manual is the official fitment chart.

http://www.rwbsmith.plus.com/citroen2/Struts/struts.pdf

I think that in about 87 Citroen got the taxation class of a small engined car down by fitting it with even smaller tyres. Don't think it was the 16.

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Post by MULLEY » Tue Mar 20, 2007 9:17 pm

Ive had a thought about this, could it be that Citroen were wanting to max the list price of their cars & hence fitting smaller tyres (they cost less) would save them a bundle on the thousands they were selling???

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Post by stuart_hedges » Wed Mar 21, 2007 9:42 am

My mum's old Pug 309 came with 145's - supposedly as an economy measure for the motorist (fuel-saving) but I always thought it was more of an economy for Peugeot. It handled like a pig until I put 165s on it.

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Post by cacaolat » Wed Mar 21, 2007 9:47 pm

My auto has 175 Michelins...I was wondering why the auto spec has only 155....Most people would not believe me but I was considering putting 155's on when my current tyres need replacing....
I always thought of citroens being stable in corners even with slim tyres..because of the good suspension. I remember my GS had 145's...
former BX 16 TGS Meteor Auto owner. No space or time to do own repairs. My BX is now owned by another member of this forum.

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Post by Philip Chidlow » Wed Mar 21, 2007 11:07 pm

So is that 175/70 R14? Or does it reduce to 175/65R14?
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Post by MULLEY » Wed Mar 21, 2007 11:22 pm

i dont think it makes that much of a difference, i personally prefer the lower profile tyre as it should have more grip. Infact why not just fit some 185/60's, thats whats on my TZD?????

I think mine originally had 165/70 or 75's on, absolutely lethal in the wet, probably didnt help that the make of tyres were budget offerings though, perhaps good tyres in that size may have been better??

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Post by cacaolat » Thu Mar 22, 2007 9:27 am

I will have a look and let you know, 175/70 or 80 ?.
Mulley, there is one situation where slimmer tyres are better and that is on snow. ... me being from the Alps have experienced it a few times. (of course it depends on the brand as well)
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Post by jeremy » Thu Mar 22, 2007 9:50 am

I think the grip is largely dependant on the area in contact with the road as well as the rubber used. In the dry the pattern would seem to be immaterial as Grand Prix cars use slicks but in the wet things are rather different.

The tyre structure is important for keeping the tread in contact with the road and the lower the sidewall the better the tread is controlled (within limits)

However nothing is simple - and in the wet the pressure of the contact with the road becomes important as well it seems - so a bigger tyre with more contact area is more prone to aquaplaning whereas a skinny tyre will cut through the water.

The other thing to be considered is the behaviour of the contact area under sideways force. We've all seen radial tyres parked partly on a kerb - with the unsupported bit sitting relatively straight. Imagine a car going round a corner - and - yes it leans - and - eventually - that lean is transmitted to the tyre - and - in the extreme the inside edge will start to lift - and then you get a rather exciting breakaway.

Originally radial tyres had an aspect ratio (tread width to wall height) of 80%. Many modern 'liquorice' tyres are about 40 or 45% - and while giving a sharper response as the small walls don't absorb much steering movement, they are even less able to keep the tread in contact with the road under cornering forces than a tyre with a higher aspect ratio - so if you do overcook your cornering the thing will let go more suddenly.

So within reason more tread in contact with the road is a good idea - and this comes from width and length - which is dependant on the circumfrence of the TYRE. When playing around with different sizes the overall diameter is something to be considered and also affects the speedo accuracy. What I suggest you should be looking at is a combination of wheel diameter, tread width and aspect ratio which gives virtually the same circumfrence - and so avoids speedo problems and also arch fouling by the tread (not walls necessarily) as well as maintaining the steering geometry (Watch the offsets of replacement rims)

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Post by MULLEY » Thu Mar 22, 2007 7:15 pm

cacaolat, i totally agree with you regarding tyre width in the snow, my little polo was ace in the snow, narrow tyres are just the job.

I am currently running 185/60 Winter Tyres & have found them to be very good, so they will be even better than thin summer tyres in the snow as the compounds are totally different.

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Post by cacaolat » Sat Mar 24, 2007 7:46 pm

Philip, yes I finally looked at the tyres of my car yes the are 175/70 R14 Michelin Energy's
former BX 16 TGS Meteor Auto owner. No space or time to do own repairs. My BX is now owned by another member of this forum.