Advice on engine gearbox upgrade for a 16"

[Aidan]

full aspect ratio tyres have a ratio of between 80 and 85%, I believe 185R14C equates to 83%, that's what Baxter put on his original tyre calculator and what I use on my gear ratio programme and it seems to be pretty accurate, probably with larger diameter rims and wider profiles it will be 80% or close to

Al, I need to get this gear calculator up on the web site as it can't easily be sent in a zip file by email as most mail servers seem to prevent zips and .exe files being transferred in order to prevent malware etc...

[lloydy]

Thats what mine wear at the moment, say's on the sticker in the door 195 16 and 205 16

I'm sure i remember something from somewhere saying that if there is no profile mentioned on a tyre size ie 195/16 or 205/16 then it is an 80 profile.
This might be wrong...someone with more knowledge might have different info.

Which at a guess would be taller than a 215/70/16. That profile percentage makes a BIG difference.

Funny, i've just been working out the same thing on a tyre calculator. 225 75 16 is only 1% larger than the 205 tyre option. Is 225 an ok width for a standard 16" by 5.5" rim?
Sorry if this is hijacking the thread

[syncropaddy]

Thats what mine wear at the moment, say's on the sticker in the door 195 16 and 205 16

I'm sure i remember something from somewhere saying that if there is no profile mentioned on a tyre size ie 195/16 or 205/16 then it is an 80 profile.
This might be wrong...someone with more knowledge might have different info.

Which at a guess would be taller than a 215/70/16. That profile percentage makes a BIG difference.

Diameter of 205/16 = 734mm
Diameter of 217/70/16 = 707mm

With all this ratio/final drive/wheel and tyre swapping, dont for get your speedo will never be the same again! Mine is out by 16% (slow)

[lloydy]

Yep and 225 75 16's are only 10mm bigger (1%) Lucky i didn't buy the 205 70 16 size a month or so ago, would have looked like low profiles!

[Russel]

225 75 is not stricktly legal on a 5.5 rim should be on a 6 rim.
See if you can find 215 85 16's that will help with gearing.
Russel

[lloydy]

Hmm there is no straight forward swap is there? Seen people with 215 70 16. but these are slightly smaller than even the 195's
Is 225's a big no no? As in garages won't fit them or is there a few people with them. ( do they run the risk of popping of ) I'm suprised there is'nt a normal size people use like on a 15" wheel

[syncrosimon]

Standard size 205 80R 16's on standard VW 16" rims.

[lloydy]

cheers for the pic

[Russel]

Places may fit them and they wont just pop off but 5.5 is not a given size by manufacturers so insurance comps wont like it.
Russel

[syncrosimon]

According to the dyno chart I am getting 64mph at 3730 and 85mph at 4920rpm (with no tacho the operator chickened out well before the red line). Thats with standard wheels and tyres on an AVR gearbox with 5.43 diff.

[jed the spread]

Blimey, thats revving quite high then isnt it. The same gearbox on a 14" van running 15" wheels must be awful on the motorway.

jed

[syncrosimon]

I find it is about right, as max torque (which is where the engine is running at peak efficiency) is at the dyno 65mph which is real world 70mph. This is where I spend most time at on the motorway with power in reserve for overtakes, and a good compromise on economy.

[jed the spread]

I find in my doka its not to bad if I drive about 65mph (not doing the same revs as you though) and dare I say not unbelievable expensive to run, its just round town where it sucks.

jed

[syncrosimon]

with the weight of my syncro I dont think the DJ could handle any higher gearing. If I stay above 65 she will go up any hill, and I can only get to 60 in 3rd, so momentum is everything.

[bigblue16]

From what you want 90kph in a heavy syncro i think 5.43 would be best with a 0.70 4th gear, will still give good speed without over revving. a 4.86 with a 0.7 would make it not nice yot drive aroung your speed of 90 kph but would be better at higher speeds. MTDI is way to go, its only disadvantage is cost. its advantages over jx/aaz are much more low end torque, much better economy, none of the getting hot problems as with AAZ.

Thanks for the input Andy but there seems to be a bit of confusion. I currently cruise at a max of 90KPH but would like to up this to about 110KPH by going with an uprated 1Z mTDi together with a 5.43 R&P and a 0.7 4th gear as you suggested. I am worried that a 4.86 R&P may be a bit of a reach and if I find I have the power reserve to go higher I can always use bigger tyres for that. (Currently running 195/75/16)
Does anyone know where in the rev band the max torque for a 1Z is, and am I right in assuming this is where the max cruise speed should be? Knowing where to put the max cruise speed would enable me to get my head arround these gear ratio calculations a bit better.
The spreadsheet built by Tim Smith is apparently for a 2.1 WBX can someone tell me where the specs for a 1z mTDi would go i.e. where does the green band start and finish, where is most effective cruise RPM etc?
Cheers Scott