Can i put bigger tyres on the back axle of a van

[s410man]

Vw lt van
Want to up the gearing a bit to make cruising nicer
Can i just change the back tyre size or will it be dangerous under braking

Don't really want to change the fronts as it's got a very good turning circle

Obviously it's only rear wheel drive

Cheers

 

[octo0072000]

depends if bigger tyres will fit/clear when loaded and what LT is it
of can you get a higher /longer diff ratio
to bring the revs down for better cruising
not sure about LTs but transits used to have different diff ratios on the atlas axle

 

[the snooper]

Also you would only have a spare yo fix one axle should you get a puncture as you can't mix sizes

 

[W.olly]

Yes as long as they clear the chassis and body work.as Octo says.

For a spare i would just carry a can of tyre fix and a spare of choice.

There are good calculators online to work out what diameter to go for to match what speed you want..

 

[keithski122]

Don't know if an it van has abs but it could affect that.Not sure on the spare tyre problem as space savers are diiferent sizes to normal wheels.I've changed the tyres on my beetle to slightly different sizes front to rear I also carry a different size spare.

 

[CompoSimmonite]

Unless the alternative tyres are a significantly larger dia then it's not going to make much difference to the speed.
Diff change is the way to go - along with recalibrated speedo.

 

[wookie]

Unless the alternative tyres are a significantly larger dia then it's not going to make much difference to the speed.
Diff change is the way to go - along with recalibrated speedo.

If you're only increasing your tyres by about 10% then all you'll probably do is make your speedo more accurate as they usually exaggerate your speed.

Of course your best bet is to check your speedo against a sat-nav as they usually more accurate than a speedo, you need to drive at as constant a speed as possible on a nice straight road as the sat-nav only works out speed based on time from one point to another so any big changes in direction or speed will give false answers.

 

[Bill Edwards]

ABS might get quite upset if it's got it.
Speedo will give slightly different readings, though they usually read under in the first place so may actually even up!
You need to look at the wheelarch clearance when the vehicle is loaded and goes bouncing all the way to the bump stops to make sure the tyre won't foul anything.
In theory the rear brakes will be slightly less effective, if it's got a brake load/compensate valve you could be clever and adjust it to make them slightly more effective to match. Unless you're going silly with the size change it probably won't be a problem.

Don't expect a massive difference in cruising speed per revs unless the change is big, but it can help.

 

[BarrieJ]

I honestly don't think changing the rear wheel/tyre size would make a noticeable difference, and potentially might create all sorts of other problems; handling, stopping and having to inform your insurance company. Who for sure would look at that as an opportunity to reassess the risk and with it how much more they can squeeze out of you.
An alternative differential would definitely sort it but I'm totally unfamiliar with the VW LT, so don't know what was available as an option when new, if any.
Was the axle shared with any other vehicles? Early LTs shared their diesel engines with mid 80s to mid 90s, 700 and 900 series Volvos.
A higher diff would give you a better cruising speed but at the loss of pull on a lower speed/high load on hills. Would that be an issue?

Somebody at this site with a similar problem:
http://www.brick-yard.co.uk/forum/lt-diff-ratio-or-5th-gear-increase_topic51631.html

Another site that might be useful, although only for 1st generation LTs, give you some idea about wheels etc.,:
http://vwlt.co.uk/wiki/vw-lt-mk-1-buyers-guide-1975-1996/

And another, dealing with alternative diff ratios: http://www.vwt4forum.co.uk/archive/index.php/t-328893.html

 

[Johnseat]

You won't gain any noticeable speed difference at that size.
You'll see the difference on a set of tachograph rollers when checking the circumference and a slight increase in the figures.
Also when you start to change the tyre size from the other axle the ABS will have a hissy fit at motorway speeds as the measured wheel speeds will be 5mph or more different when driving in a straight line, the ABS system will shut down, that's if your van has ABS...

The only ways are to change the final gear ratio in the gearbox or swap out the diff but then you can scupper the power when driving up steep hills, I've had a van with a swapped out rear axle for the owner to moan about how it no longer pulls up hills due to the increasing diff ratio. Saying that it was fantastic on juice at motorway speeds.

 

[roofman]

I think the OP wants a more relaxed cruising RPM and not more speed...ive done this on one of my cabstars by using a taller section rear rubber. Dropped the RPM,s by 600 and made for a nicer relaxed 60-65mph

 

[s410man]

I honestly don't think changing the rear wheel/tyre size would make a noticeable difference, and potentially might create all sorts of other problems; handling, stopping and having to inform your insurance company. Who for sure would look at that as an opportunity to reassess the risk and with it how much more they can squeeze out of you.
An alternative differential would definitely sort it but I'm totally unfamiliar with the VW LT, so don't know what was available as an option when new, if any.
Was the axle shared with any other vehicles? Early LTs shared their diesel engines with mid 80s to mid 90s, 700 and 900 series Volvos.
A higher diff would give you a better cruising speed but at the loss of pull on a lower speed/high load on hills. Would that be an issue?

Somebody at this site with a similar problem:
http://www.brick-yard.co.uk/forum/lt-diff-ratio-or-5th-gear-increase_topic51631.html

Another site that might be useful, although only for 1st generation LTs, give you some idea about wheels etc.,:
http://vwlt.co.uk/wiki/vw-lt-mk-1-buyers-guide-1975-1996/

And another, dealing with alternative diff ratios: http://www.vwt4forum.co.uk/archive/index.php/t-328893.html

Hadn't actually thought about the abs!!

I have read the first 2 links previously but the third one with the axle numbers is just what I'm after!!

Think i might try a different diff once i find out what mine is

It's a 109hp one so should handle a better ratio easy enough

Thanks so far everyone!!

 

[Justme]

It will stuff up your gearing / acceleration / MPG.

 

[wookie]

It will stuff up your gearing / acceleration / MPG.

It might stuff up your MPG, but then again if the vehicle is undergeared to begin with it could improve your MPG.

Tr7's for example (I mention because they are a favourite of mine and consequently I know a fair bit about them) originally had a 4 speed box and had an undergeared diff that makes them "more sporty" to drive, but if you increase the rear diff ratio it massively improves the car, 1st gear becomes more useful, it drops the revs for any chosen speed so it's nicer to drive and you get better MPG when cruising.

 

[Justme]

Newer vehicles are much closer to the right gearing out of the factory.

 

[CornishPete]

I once bought some wheels/tyres off ebay for my t5 and when delivered they weren't the size advertised. The tyres were about 1" bigger in diameter. I couldn't be arsed with the hassle sending them back so I used them anyway. Did about 15000 miles on them and didn't notice any difference when driving. Abs was fine too.

 

[MBB]

Fitting different size wheels may compromise your insurance if you have accident. Insurance co's will do anything to stop paying you.

MBB