TDI300 auto - Taller tyres, what you reckon?

[stumps]

Hi all. New with a D1 '97 TDI300 auto. I have read over a year of forum posts getting myself up to speed on issues, the good, the bad etc. What a great collection of info and good comradery of the group.

So I have finally got to drive mine on the open road at freeway speed and wow!... was surprised just how low it revs in 4th lockup...and there in is my concern. I wanted to get some taller tyres above the 235/70/16's I have with say 215/85 16 (like diff clearance more than width ;) ). But now I am worried by the risk of it being way too tall a gearing for the little 2.5...even with this modest increase. I do not want to see any -ve fuel economy or engine torque/power issues. Also if I went with this set, will a camel cut be required?

Thanks for any opinions or experience on this.

[seano87]

245/75R16 is pretty common for a small increase in tyre height. Typically makes speedo read almost dead accurate too.

235/85R16 also a common choice and the auto should cope with it fine, particularly if the engine is pretty healthy. At this point though the gearing can be pretty close to its limit though.

245/75 may fit with no camel cut on the rear with a 2" lift (mine was fine). 235/85 will almost certainly require a camel cut.

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[seano87]

PS. 215/85R16 will only get you an extra 1.5cm or so under the diff. Wouldn't have thought that'd be worth it?

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[stumps]

PS. 215/85R16 will only get you an extra 1.5cm or so under the diff. Wouldn't have thought that'd be worth it?

Sent from my Galaxy Nexus using Tapatalk 2

Thanks seano87....great info! Yes, the donk is in good nick...reco'd 30k ago. I was thinking of a steel set with more aggressive offroad tyres and have the alloys with existing 235/70s 'road profile' for the mrs around town. Yes I understand the minimal height gain, but the way this thing revs, I thought it may be the realistic limit. Last thing I want is an overloaded engine.

[Vern]

WE put 235/85's on our 300tdi disco, made the world of difference, is so much better to drive. It actually feels like it should be geared like this.

[loanrangie]

265/70's on mine and as Vern says the larger tyres do seem to make it go better, pickup is definitely improved over the original cheese cutters.

[edddo]

I run 31inch ( very close to same rolling diameter as 245-75 and 215-85) and acceleration and hill holding suffers for sure in comparision to standard size. Avg EGT and fuel consumption is a bit higher too, as I would expect. Surprised others are finding otherwise.

[Judo]

I've got 245/75's on my D1 (manual). I definitely noticed that I need to give it more juice going up hills and taking off. Fuel economy has gone from 10L/100 on 205/80's to 11.5L/100 on 245/75's.

I suspect there's a lot of people will disagree with me, but if you are really concerned about less power and worse fuel economy, stay with 235/70's. As much as I'm loving the tyres, I'm really 50/50 on whether I would choose them again with the 300TDI. It just needs ever so slightly more power for hill climbs....

Also you WILL need to camel cut with 245/75's. I don't understand how anyone can have 245/75s and not.... as far as I can see, you WILL hit the guard on rear suspension compression. I drove back from the tyres place without a camel cut and that was fine, but compressing the wheel up into the arch would hit the guard IMO.

[dullbird]

I've got 245/75's on my D1 (manual). I definitely noticed that I need to give it more juice going up hills and taking off. Fuel economy has gone from 10L/100 on 205/80's to 11.5L/100 on 245/75's.

I suspect there's a lot of people will disagree with me, but if you are really concerned about less power and worse fuel economy, stay with 235/70's. As much as I'm loving the tyres, I'm really 50/50 on whether I would choose them again with the 300TDI. It just needs ever so slightly more power for hill climbs....

Also you WILL need to camel cut with 245/75's. I don't understand how anyone can have 245/75s and not.... as far as I can see, you WILL hit the guard on rear suspension compression. I drove back from the tyres place without a camel cut and that was fine, but compressing the wheel up into the arch would hit the guard IMO.

Yep agree with everything said here as its the same for me except I'm in an auto not a manual

[jazzaD1]

decreases in fuel economy may not be as drastic as they seem, as with the larger tyres, you will travel further than your odometer will read, skewing the fuel economy figures somewhat

[Judo]

decreases in fuel economy may not be as drastic as they seem, as with the larger tyres, you will travel further than your odometer will read, skewing the fuel economy figures somewhat
That's true, I always forget about that! The length of a kilometre changes. :D

[ade]

ive got 225/75/16 on my stock 95 disco seems to like it

[stumps]

Thanks for all the comments, good info. I don't think I will go any larger than 245/75/16 or 215/85/16...at the most for now. Maybe there's more value in a rear diff lock than the extra clearance! ;)

[steveG]

Had 245/75's on ours (300tdi/auto).
Only thing that used to bug me a bit was getting going when towing our Jayco camper. Felt almost dead until it started to build boost at around 1800 RPM. Learnt to live with it.
Great apart from that, and probably a fuel pump tweak would have improved things but I never got round to it before I sold it.

Steve

[redrovertdi]

My 300tdi 110 defender with zf4hp22 auto and disco transfer case drives 265/75/16 fine, only down side is box hunts between lock up in an 80km zone.

[CU55TM Disco]

I have the above tyres (265/75-16) on a 300TDI disco with ManWell. 2500RPM is the magic mark, returning about 10.5 to low 11's. Towed a renta-car trailer back from syd with a 121 Metro on board and returned 11.2/100.