Larger tyres and diff damage in 80 series Landcruiser? (1 Viewer)

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Joined
Dec 29, 2022
Threads
3
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Location
Sydney.Australia
Hi folks

A few months back I got new tyres on my 1990 HZJ80R Landcruiser and wound up with 35" all terrains, as the shop said they couldn't source the 33" ones that I previously had. Yesterday a fellow Cruiser owner asked me if I was worried about the possible diff damage, as he had heard of instances of diffs being damaged and even broken by larger tyres. This is the first I had heard of this, and the shop certainly didn't flag it, although they may have just been interested in upsizing the sale... All they flagged was to be mindful of the difference on the speedo and odo.

All I've been able to find online is a generic article stating this:

"Everything that indirectly attaches to your tyres is put under more stress when you fit bigger tyres. This includes your CV’s, steering box, steering shafts, axles and differentials. Many people will not break components on standard tyres (especially CV’s) but as soon as they go up a few tyre sizes the breakages happen on a regular basis." (Fitting bigger tyres to your 4WD; what should you consider? - https://www.4wdingaustralia.com/4x4/fitting-bigger-tyres-to-your-4wd/)

Has anyone encountered or heard of this issue, or know of any other factors that might make such damage more likely (so that I can avoid or minimise those factors)? I'm pretty keen to not destroy any bits of my truck and well annoyed that the tyre shop didn't know or care to mention it :mad: I'm kinda tempted to go to another shop to swap back to 33s, cut the loss and try to sell the 35s if the risk is substantial.

Many thanks for any insight!
 
Bigger tires will stress the drivetrain more. Weather or not it causes a problem comes down to how you drive it.
Hammer down all the time, and you'll probably be breaking stuff. Drive like a normal person and you probably wont.
 
itll be fine it's a landcruiser, might make you a bit slower though
if it was a jeep with a dana 30 i'd be worried

What it does do is put you outside of the ideal gearing in your diffs.
If you wheel it hard and have a front locker i would suggest upgraded bifs and axle shafts (longfields, rcv etc)
 
itll be fine it's a landcruiser, might make you a bit slower though
if it was a jeep with a dana 30 i'd be worried

What it does do is put you outside of the ideal gearing in your diffs.
If you wheel it hard and have a front locker i would suggest upgraded bifs and axle shafts (longfields, rcv etc)
I've noticed it's a bit slower and also seems a bit underpowered when travelling at speed - harder to maintain speed uphill in particular. And yeah, the gears feel weird.
 
You can break stuff with 33s too…search for threads on breaking the front diff when reversing under load. 80 series section will get you more results and responses.
 
your speedo will be out of whack, 33's for example will read 100 kph on the dash but youre really doing 103 - 104 so 35's a bit more
a little more stress on wheel bearings and as youve discovered your gearing suffers.
But, your economy on long highway driving should improve as the wheels turn less to cover the same distance and vice versa with around town - your economy suffers getting the larger tyres up to speed

ultimately if you re gear the diffs you can have the same take off, economy overall and feel as running standard size tyres

if you drive it normally you shouldnt really have anything to worry about
 
Hi folks

A few months back I got new tyres on my 1990 HZJ80R Landcruiser and wound up with 35" all terrains, as the shop said they couldn't source the 33" ones that I previously had. Yesterday a fellow Cruiser owner asked me if I was worried about the possible diff damage, as he had heard of instances of diffs being damaged and even broken by larger tyres. This is the first I had heard of this, and the shop certainly didn't flag it, although they may have just been interested in upsizing the sale... All they flagged was to be mindful of the difference on the speedo and odo.

All I've been able to find online is a generic article stating this:

"Everything that indirectly attaches to your tyres is put under more stress when you fit bigger tyres. This includes your CV’s, steering box, steering shafts, axles and differentials. Many people will not break components on standard tyres (especially CV’s) but as soon as they go up a few tyre sizes the breakages happen on a regular basis." (Fitting bigger tyres to your 4WD; what should you consider? - https://www.4wdingaustralia.com/4x4/fitting-bigger-tyres-to-your-4wd/)

Has anyone encountered or heard of this issue, or know of any other factors that might make such damage more likely (so that I can avoid or minimise those factors)? I'm pretty keen to not destroy any bits of my truck and well annoyed that the tyre shop didn't know or care to mention it :mad: I'm kinda tempted to go to another shop to swap back to 33s, cut the loss and try to sell the 35s if the risk is substantial.

Many thanks for any insight!
I think you're correct about the shop you purchased the tires from ("just been interested in upsizing the sale"). 33's are more common than 35's, so I would bet they were pushing the 35's. Do you have a lift installed? Reason I'm asking is that, as you may have noticed already, 35" tires on a stock 80 can rub on front fenders and wheel wells when the tires are stuffed or cranked on sharp turns. Rears can also contact wheel wells on bumps if rig is fully loaded for a trip. The OME 2.5" (or equivalent) works well for 35's. I realize you're in OZ, but most reputable tire shops here in the US will discourage customers from buying tires that will likely have clearance issues. As far as issues, the 80 series, being overbuilt still holds up well with 35" tires as long as you're regular with your maintenance. Since running 35's on my '94 gasser, I added the Yellow Box to fix the speedometer and changed the gears in my diffs to reclaim power. You can run the stock gears and live with it, but I tow an off road trailer.
 
I think you're correct about the shop you purchased the tires from ("just been interested in upsizing the sale"). 33's are more common than 35's, so I would bet they were pushing the 35's. Do you have a lift installed? Reason I'm asking is that, as you may have noticed already, 35" tires on a stock 80 can rub on front fenders and wheel wells when the tires are stuffed or cranked on sharp turns. Rears can also contact wheel wells on bumps if rig is fully loaded for a trip. The OME 2.5" (or equivalent) works well for 35's. I realize you're in OZ, but most reputable tire shops here in the US will discourage customers from buying tires that will likely have clearance issues. As far as issues, the 80 series, being overbuilt still holds up well with 35" tires as long as you're regular with your maintenance. Since running 35's on my '94 gasser, I added the Yellow Box to fix the speedometer and changed the gears in my diffs to reclaim power. You can run the stock gears and live with it, but I tow an off road trailer.
Hiya

The rig does have a lift kit and I've not noticed rubbing, but I've not done any serious off-roading on these tyres. I don't like how it's handling on the 35s though - the braking is slow, cornering on windy or dirt roads feels like we're teetering, the power is diminished, and it's skated on a wet freeway when braking. I'm loathe to start an avalanche of mods to try to make these tyres work, when they weren't what I wanted or needed. I'm going to downsize back to 33s and try to on-sell the 35s. They've not done many km or rough stuff, so hopefully I can recoup some of the loss.

There's also the kay issue that the rig is illegal with a 2" lift plus the 35s, which voids my insurance. No point spending extra time and money to modify it when it's worthless if crashed (gods forbid) and could get ticketed by a finicky enough cop at any point.

I went back to the shop and the manager tried to start an argument with me about loads and speed ratings when I said the tyres make the rig illegal. He clearly didn't know there was a legal height limit and started trying to explain that the tyres were physically capable of keeping the truck safe, rather than accept that that's an irrelevant point because it's simply illegal, given the existence of the lift kit. I told him I'd had a conversation with another Cruiser owner who said there is a local cop who loves ticketing people for this stuff, and he said "no, they don't do that." Uh-huh, sure, my friend. You clearly know better than the actual driving community... He also kept mentioning that the truck has done over half a million km, like that's in any way relevant. No positive shop review from this camper :mad:

cheers
 
Hiya

The rig does have a lift kit and I've not noticed rubbing, but I've not done any serious off-roading on these tyres. I don't like how it's handling on the 35s though - the braking is slow, cornering on windy or dirt roads feels like we're teetering, the power is diminished, and it's skated on a wet freeway when braking. I'm loathe to start an avalanche of mods to try to make these tyres work, when they weren't what I wanted or needed. I'm going to downsize back to 33s and try to on-sell the 35s. They've not done many km or rough stuff, so hopefully I can recoup some of the loss.

There's also the kay issue that the rig is illegal with a 2" lift plus the 35s, which voids my insurance. No point spending extra time and money to modify it when it's worthless if crashed (gods forbid) and could get ticketed by a finicky enough cop at any point.

I went back to the shop and the manager tried to start an argument with me about loads and speed ratings when I said the tyres make the rig illegal. He clearly didn't know there was a legal height limit and started trying to explain that the tyres were physically capable of keeping the truck safe, rather than accept that that's an irrelevant point because it's simply illegal, given the existence of the lift kit. I told him I'd had a conversation with another Cruiser owner who said there is a local cop who loves ticketing people for this stuff, and he said "no, they don't do that." Uh-huh, sure, my friend. You clearly know better than the actual driving community... He also kept mentioning that the truck has done over half a million km, like that's in any way relevant. No positive shop review from this camper :mad:

cheers
Sounds like that tire shop manager isn't qualified to do his job. And that's unfortunate, that you've already done business. I agree that the 35" has no advantage to most driving, in fact some disadvantages like you've mentioned. It's ironic, but some 80 owners put up with the bad to get that little bit of good, off road. In your case, being illegal, you don't really have a choice and are stuck with this tire shop's (claimed) ignorance of your laws, if you want to remain legal. It's a shame that there's not a avenue available that would allow you to demand this tire shop make it right! It's not like you went into the shop with the intention to purchase the 35" tires. Sounds like you were just intending to replace what you had: "as the shop said they couldn't source the 33" ones that I previously had." I think that was an out and out lie by him, but you'd need some help to prove it. The managers claims of "loads and speed ratings" were not requested by you in your purchase, but were pushed on you to try and butter you up and side track you to his illicit way of doing business. This shop's methods need to be public knowledge to help destiny take its course.
 
your speedo will be out of whack, 33's for example will read 100 kph on the dash but youre really doing 103 - 104 so 35's a bit more
a little more stress on wheel bearings and as youve discovered your gearing suffers.
But, your economy on long highway driving should improve as the wheels turn less to cover the same distance and vice versa with around town - your economy suffers getting the larger tyres up to speed

ultimately if you re gear the diffs you can have the same take off, economy overall and feel as running standard size tyres

if you drive it normally you shouldnt really have anything to worry about
Many thanks for the info - that's all good to know. I've swapped back down to 33s though. Makes life much simpler, and I sure won't be dealing with that tyre shop again.
 
You can break stuff with 33s too…search for threads on breaking the front diff when reversing under load. 80 series section will get you more results and responses.
Yikes - good to know. We don't do much towing, so hopefully will be OK back on 33s.
 

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