Club 80-90 Forums

very happy with a 1.9 diesel engine in my previous 1.7 though the revs a bit high in the first 3 gears, have read that increasing the wheels to a 15 inch will help this, but have heard of others putting 16inch on. which are best please?

Depends as much on the profile of the tyres, the aspect ratio. For the same Aspect Ratio, 15's will make a bit of difference.

15s are more common and usually a wide range of tyres can be had... you do need to gear up with the 1.9 (turbo?) as you suspect.
My AAZ has Vmax = 3600 stamped on the cambelt cover - with 15" macho off-road tyres (tall) it has gone from easily over-evving in top (4000+), to slightly overgeared -maybe needs a bit more poke up motorway hills sort of thing (intercooler). On the flat I cruise it at 3750, just over 70, about right? Vmax I interpret as a conservative continuous rating, as it goes well over 4000 from time to time through the gears.

But they are very tall for 15s, if you go lower profile, you might even not gear up at all. Remember its not 1" in 15 difference, its 1" in the overall tyre height, so for same AR, that's only about 1 in 25, 4%

From the road-going 14s it had, I've probably geared up about 8%

i think i understand what u are saying. that its more to do with the type of tyres as the size of wheels. i am being offered a full set of 15" merc wheels with good tyres or a pair of 15" wheels with the best type of tyres to get the most ut of the gears. im not sur e which is best? also i will now have to check how tall they are to get the better gear ratio.

what im asking is should i change all the wheels or can i just change the rear two to get beeter ratios?
thanks

All 4, owise handling will change (guess oversteer) & need 2 spares

Didn't think you were thinking along these lines, not many do this, if any?

Is it turbo?

I have recently changed to aaz engine and am in the process of finding out as well.
If you decide to change for 15" , change the four wheels. The spare might not fit in the cradle but would be ok as a take me home. Dont know about MOT .

your speedo takes information from the front wheels. So keep the original wheel in the front while you are trying stuff at the back. If you have a rev counter it ll allow you to compare between 185 /80/14 and 195/80/15 for instance which i think might just do it for me. this should lower the revs a fraction for the same speed and still go up slopes without dropping in fourth. You could also try 195/80/14 and may be that would be enough. cheap to do anyway.
And of course once the conversion is done you will be looking to rstore the accuracy of your speedo, but thats another story......
Are there any other steel wheels that would fit without modification? What about wheel covers?

Look at this site for working out tyre sizes, put in standard size on one line then try different on the other, it gives you a % increase difference

http://www.tyresave.co.uk/tyresize.html


I use 195/80/14 on mine and it does increase gearing a bit.

Or this one...

http://www.club80-90syncro.co.uk/Syncro ... %20rpm.htm

TRC calculator down the bottom;
Most of those FD diff ratios will apply to 2WD's as well

At least 5% should be about what you want

hi mate, is it a 1.9D non turbo engine you have changed too?
just wanted to know how much of a difference to your power it has made as i cant decide to fit a non turbo (1Y) engine which i already have or go for a turbo motor.

cheers

HarryMann wrote:Or this one...

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At least 5% should be about what you want

Thanks for the figure HarryManm. After a lot of thought this afternoon i came to the onclusion that under 3 percent wasnt worth it and 9 or 10 perhaps optimistic. So you must be on the ball. I also went to see a mate who fit tyres in a garage in the middle of nowhere. We tried a wheel from a merc 15 " c class. It does bolt on ( tried it on the front) but the metal rim rubs badly on the wishbone!!? I thought these were ok! Anybody for some feedback?

The Tyre specialist thought 185/80/15 would be ok . Thats just under 4% and a good selection of tyres to be had. From what he says 195/80/15 are "jeep" tyres, freelanders and such like. Less choice.gain of 6%. Also good choice in 195/80/14 but that is only just above 2% gain

HarryMann wrote: My AAZ has Vmax = 3600 stamped on the cambelt cover - with 15" macho off-road tyres (tall) it has gone from easily over-evving in top (4000+), to slightly overgeared -maybe needs a bit more poke up motorway hills sort of thing (intercooler). On the flat I cruise it at 3750, just over 70, about right? Vmax I interpret as a conservative continuous rating, as it goes well over 4000 from time to time through the gears.

With 185/80/14 here are some readings I took in 5th gear in Km/h
60km/h=2100... 80km/h=2800... 90km/h=3200..... 100km/h=3500 ... 110km/h=3800.... 120km/h=4200.... 130km/h=4500(max speed)

So we seem to get the same results at 110km/h (70 mph) and yet i havent changed the tyres and you have:? Should I be delighted or what?

195/15's are Suzuki Jeep tyres, and from what I remember they are very close to the rear wishbone.

Those C class wheels come in various offset, ET 37 I've got on my syncro as have a few other.

They also come in ET33/34 ? considered ideal match for T25

Maybe you have some that have a higher offset... ask DH, he knows about those wheels I think.

My ET37 with 15" Greenway machos, have never rubbed, even crashing down hills and full of mud, but syncro a bit different at the front of course. Didn't think though that this would matter in this context.

Yup, cruise anywhere between 3650- and 3800, maybe 3900 with a following wind, I do get bored much below 70, but others will say I'm caning it - she's still goiug though

Your gear box must be way shorter than the one fitted to my van if your getting the same ratio speed/ rpms after tyre mods. The point where you are at the mo is where i am starting and it will probably be slightly different for every type of van.

I would really like some good looking 15" steels similar to the originals.

Orig. 1.6TD Diesel Doka Syncro

Trans code AHF(?) 5.43 with 0.78 top gear, some of the single cabs have 5.83

What is your gearbox code? Check here if you don't know it.. or if you do even, this gives the lowdown on top-gear indirect ratio too..

http://www.club80-90syncro.co.uk/Syncro ... _Specs.htm

Don't forget this slightly clapped engine is pulling along something sitting maybe a foot higher than a 2WD, on 4 knobbly Greenway Machos through a 4WD drivetrain, and a draggy DoKa body.
With a 5.43 and maybe 6-8% higher thro' tyres, gives 5.07 equiv. and struggles in a wind or gradient a bit. Have seen 4050 in top.

Don't ignore the indirect top ratio, either .78 or .85 (9% difference in top)

The only really accurate way is to measure the TRC as described in the first ink, few mfrs quote this figure readily, and there's always slip at 50mph and above. Roll it about and count 10 revs to a chalk mark if you really want to compare two tyres accurately (the slip will be about the same).

jeepster regards the engine swap. im very happy with the increase in power of the 1.9 straight diesel swap. i have more power in evry gear than my previous 1.7, which was good at pulling away, but slow on moterway. i havnt really opened the 1.9 up yet i have touched on 60, but have yet to moterway drive it. i pondered on turbo or non turbo and after research i decided on non turbo as its less to worry about and les maintence, i reckon. and personally i would worry about braking as with the 1.9 there is a very noticable improvement in performance, and this has to put more of a strain on the original braking system. i would personally question putting a turbo 1.9 in without improving the braking system some how. its all down to choice, money and availabilty. my transfer cost me around £800 with myself doing half the conversion and engine removale. i guess you need to spend more with a turbo as there are more modifications to do, such as altering a engine mount, but u will need to ask someone who has converted to a turbo. hope this helps.