JX to AAZ - bigger tyres???

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bidbid14
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JX to AAZ - bigger tyres???

Post by bidbid14 »

Hi all,

I replaced my 1.6TD JX engine with a 1.9TD AAZ a couple of years back. I kept the old gearbox
I'm really pleased with how it's running but I get very high revs - 1st gear non existent and into 5th by 30mph - I've got used to it now but...

I saw something about putting bigger tyres on. Can anyone confirm if this will improve things?

Any info on this gratefully recieved. ie size of tyres and what i can expect

thanks
white, H reg, 1990 California pop top , 1.9TD AAZ

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ajsimmo
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Re: JX to AAZ - bigger tyres???

Post by ajsimmo »

I once had an AAZ powered van with stock wheels & tyres, so know exactly what you mean. I swapped to 215/75R15 on Mefro 15" wheels, and it transformed the drive for the better. Quieter, smoother, just altogether nicer without losing any pulling power. It was a Syncro so effectively a four speed (as G is too low for road use) and the gearing seemed perfect. With yours being a five speed 2WD over-gearing is even less of a worry as your ratios will be closer together, and less transmission power loss.
If you want to stick with the original 14" wheels then the biggest available are 215R14C, starting at about £55 each. They'll help a lot, but might feel a bit more blancmangey around the corners due to the very high sidewall for a smaller tyre.
See here for a useful size comparison tool (ooer)
https://tiresize.com/calculator/" onclick="window.open(this.href);return false;

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ash1293
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Re: JX to AAZ - bigger tyres???

Post by ash1293 »

The 1.9td motor should handle larger tyres without too much problem and should lower the revs for a given speed but maybe not as much as you hope. Certainly the first thing to try as changing the final drive will be a much more costly affair.

What size wheels/tyres do you have at the moment?

14" will limit tyres choice somewhat but some 195/14c & 205/14c should work on standard rims.

15" merc, mefro, alloys etc will give you a far greater choice in tyre choice, I run 205/70/15c but mine is a petrol. I have heard/seen taller fitted - poss 195/80/15 if you do not want overly wide, 215/75/15c if you do.

Just make sure you don't try and use too wide a tyre for the rim - theres a greater chance of deseating the tyre under load.
AND
make sure the tyre has correct load rating. More applicable with lower profile tyres as for the size of tyres we are talking about on here you are mostly van/4x4 sizes anyway.

Get some details up on your thread with location etc - you may get lucky as there may be someone local with a pair of rims/tyres you could try on the back.
1990 1.9DG 34DAT carb Leisuredrive hightop

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ajsimmo
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Re: JX to AAZ - bigger tyres???

Post by ajsimmo »

ash1293 wrote:The 1.9td motor should handle larger tyres without too much problem
Yes, I've just told him that. Actually it will without any problem.
ash1293 wrote: and should lower the revs for a given speed but maybe not as much as you hope.
That's what the calculator is for, so you can work out exactly what the reduction in rpm will be, rather than just hope.
ash1293 wrote: What size wheels/tyres do you have at the moment?
In the absence of an alternative being stated, I assumed standard.
ash1293 wrote: 14" will limit tyres choice somewhat but some 195/14c & 205/14c should work on standard rims.
The 195, and possibly also the 205, would not be sufficiently larger in circumference to achieve his objective, as he says revs are "very high". Hence I suggested the 215 as the largest available on a 14" wheel, which would reduce rpm by 6.5% at any given roadspeed, and the AAZ should cope quite happily with that.
ash1293 wrote: 15" merc, mefro, alloys etc will give you a far greater choice in tyre choice, I run 205/70/15c but mine is a petrol. I have heard/seen taller fitted - poss 195/80/15 if you do not want overly wide, 215/75/15c if you do.
Your tyre size 205/70/15c is only 2.3% greater circumference than the standard 185R14C, so not really a useful solution for his enquiry. I wouldn't want him to be mislead by quoting sizes inappropriate for his needs.
Whilst 215/75R15C is wider, what makes you say they're overly wide? They were great on my Syncro, smoother quieter ride, improved grip, improved economy, no adverse effects on suspension with no fouling anywhere.

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ash1293
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Re: JX to AAZ - bigger tyres???

Post by ash1293 »

Sorry, did not mean to stand on anyones toes, I was busy replying this morning before heading to work and your intial reply had just popped up while I had been typing.

All I was getting at was that fact some people hope that by fitting bigger tyres it will drop revs much more than the 5-10% that is realistically acheivable.

On standard 14x5.5" rims I wouldn't personally want to go above a 205 width. IIRC most tyre manufacturers etc state a maximum recommended width of 195 for a 5.5"

My tyre choice was just an example and not what will suit everyone.

My phrasing is a bit off and meant that a 195/80/15 would give a similar width to original , ie not overly wider than original. Simply meaning that if a wider tyre was wanted then 215/70/15 should be possible without any great issues.
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toomanytoys
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Re: JX to AAZ - bigger tyres???

Post by toomanytoys »

215r14 is about the biggest tyre that will go on a 5.5” rim. There have been quite a few running this size. “Billy numbers” has run that size for many years on the back of his Pug 2.2 powered van.
(And sorry if this seems like a blatant plug, they are going on the sale pages shortly) I have 3 firestone van rated tyres with lots of tread, to clear out. I prob have a pair (maybe 3) of wheels I can get them fitted to as well (new valves and balanced).. if interested.

bidbid14
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Re: JX to AAZ - bigger tyres???

Post by bidbid14 »

Wow! Thanks for the great replies everyone.

You'll know my van well ajsimmo as it's been to Campershack loads of times. :D (Craig in West Bridgford)

I've got the carat alloys so would like to stick with them.

All good food for thought
Cheers
white, H reg, 1990 California pop top , 1.9TD AAZ

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Re: JX to AAZ - bigger tyres???

Post by matt brighton »

Hi

I have mahoossive 225/80/14's on mine for the same reason

you can't go bigger - some would say its too big

it has the desired effect of being much less "revvy" at 70 though rather floaty around the corners ....

comfy ride though

:ok

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