Thread: Talk to me about Tyres & Towing

D2a 2004 Td5 Auto.

Was going to hold out until new year to fit new tyres, as the existing Cooper S/T (255/70*16), being only passenger rated construction, probably aren't the best choice for towing a 1200-1500kg camper with an expected ball weight of 120-140kg ..... Camper due in next 1-2 weeks. Only a couple of short local trips over Xmas planned, which would have done the Coopers for their final run .... 'cause they've done 108,000km, have plenty of tread left, but are 7-8yrs old ... AND ...

... AND coming home sunday night from Macksville the left rear decided to dissmantle itself .... tread peeled away for about 1/3rd of the tyre and deflated very quickly ..... Bugger! (time to fix some plastic trim bits and mudflap which took a flogging) Pull over, and fit the spare .... Bugger! Spare has a large bubble in it on the outer edge of the tread Fit it up anyway as it's my only spare, and limp home at reduced speed ... made it no further dramas.

So, need tyres ... like NOW. S/T's no longer made. 2x front S/T's have only 40,000km on them. 3x rears are for all intent NFG anymore ....so 5x new tyres needed.

Dilema is towing vs tyre diameter and getting the best match of tyre size for the intended duty without buggering up the gearing too much.

I have 255/70 fitted now. These are 3.8% oversize, At (on GPS/Nanocom) 80/90/100 km/hr we're doing about 1800rpm / 2000rpm / 2250rpm and loaded with 3 adults and camping gear it's capable .... need to row it along a bit before big hills but it works for me and has got us everywhere we've ever pointed it, and done it reliably AND economically. I don't want to drop engine revs to the point where we have to travel too fast to get the revs back into the sweet zone because of a tyre size increase. Comfy spot seems to be around 90-92km/hr doing about 2150rpm.

The Td5 is standard except for the wastegate being wound out to just under 20psi. Down the track there will be an EGT guage, maybe an intercooler, and an ECU remap (mild, NOT wild!) ... but for now and the near forseeable future we'll be running pretty much stock standard. There's other items need doing before the remap.

So, when I start hauling the camper, I'm expecting there to be alot more 3rd gear with the TC locked up, only using 4th/D on the flat level ground. Anticipate 85-95 average speeds (so on current tyres 90km/hr is 2000rpm). Going UP in tyre size to a 265/70 would benefit me in stretching the Disco's legs in 3rd lockup ... but is that going to be too much of a stretch in 4th/D ??? (at 90km/hr this would mean 1850-1900rpm) That would take me to about 5% oversize .... remember it's for towing. If I wasn't towing I'd be happy to go to the 265/70. I put a set of 265/70 Bridgestone D697LT on my D-Max and am suitably impressed for $265 fitted and balanced. They do a 255/70 D697LT as well ... and I'd even consider Cooper again (S/TMax) but I don't like the price!

265/70 and live with the loss of performance until we get around to squeezing some more HP out of the Td5 ?

255/70 (as now) and accept it will rev a bit higher in 3rd, which in turn will be a marginally smaller loading on the gearbox in 4th/D

Standard size 255/65 are not an option as there's not really a suitable more agressive AT in this size. The rims are 8" wide, so 245/75 in some brands are not suitable for an 8" rim.

Those of you who are already towing ... what size tow (kg) vs tyre size vs engine mods ... got a real world experience opinion for me ??

Sorry, it's a bit of a ramble, hope I've conveyed what I set out to.

Talk to me

Remember Fluids has 8 inch rims which will knock out 235X85 and in practical terms 245x75.
265x75 will be all Ok and fitted by a tyre place but is pretty big and for towing will really kill performance.

BTW 255x70 is now everywhere on ebay in road pattern as they are AFAIK stock size on the latest Ford and Mazda utes. To me 255.70x16 is ideal, although I personally would prefer 245.75 , but as a tyre place told me as they refused to fit "they will peel off the rim too easily when deflated"

So if you were stuck, you would be able to "get out of jail." with something correct size and black and round.
Regards Philip A