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166 17" Tyre pressures

5K views 25 replies 12 participants last post by  DavidP. 
#1 ·
Right, I've been driving my 166 now for nearly 4 years with it's factory fitted 17" Alloys (you know the nice ones with the roundy holes).

Unfortunetly when I bought her the previous owner didn't include all the documentation, so having rambeled around on line and as best I could I reckoned the tyre pressures should be 2.3 bar/34 psi. All was well (apart from the steering feeling a little heavy). Then, last week I had a blow out on a tyre that was less than 12 months old. Not unusual but got me back the correct pressure question.

Searching the forum (don't ask why I didn't check here first!) I discoved a thread that said the AR recomened pressrue for 17" was 2.7 bar/39 psi front and back. So I pumped the tyres up to 2.7 and ... it's terrible! Very bad cornering when pushed. Feels very, very skittish. I've doubled checked the pressures with a digital pressure gauge.

So, my question to any 166 owers with 17" is this ... what pressures do you put in? Also, have you noticed a significant difference in handling with differnt makes/models of tyre?

Cheers

Variator
 
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#3 ·
Trouble is the handbook doesn't mention 225/45/17. If you look at Jamie Porter's website - www.alfaworkshop.co.uk his forecourt guide says 2.7 bar, x 14.7 psi = 39.69 psi. A few threads have backed this up and I certainly have found these pressures to feel better on the road. I'll admit that neck end of 40psi does seem a lot on a car but it works on my bus.
 
#5 ·
My book mentions the 225/45/17 clearly stated as 2.7 bar as opposed to 2.3 bar on the 16's. It also states to increase by 0.3 when driving at sustained high speed!

When I first bought my car all the tyres were unevenly worn - I noted that tyre pressures were way low at around 2.0 Bar. I had geometry checked - No problem. I replaced tyres and run at 2.7 Bar now - Good even wear with no problems.

Problem you have noted Variator is that running with low pressure provides more cornering grip - An old trick. That is why car now feels strange at correct pressure!
 
#9 ·
I tried 39 psi and the car was like driving on a football..Bouncy all over the place and a very hard [ harder ] ride..Felt all bumps through the steering..Surely no 17" tyre can run on 39 psi..I reverted back to 32 psi and the ride is just right..Solid , hard but not bouncy anymore..
And it feels planted at high speed and corners...I dont think they wear out any quicker at a lower pressure..I had a Merc SL with 18" on..265 rears and run those with 32 psi with no problem and no uneven wear...:)
PS: As I am in a hot country, pressure tend to increase on runs anyway..:thumbs:
 
#10 ·
225/45/17 telephone dial alloys with Goodyear Eagle F1 tyres, run at 39psi feels fine to me. I certainly wouldn't describe the ride as harsh or skittish. I find the car tramlines alot but I think this has more to do with the width of the rims than the tyres pressures. The ride is also a bit wallowy, and I am considering mods to the suspension to counter this.
 
#14 ·
The ride is also a bit wallowy, and I am considering mods to the suspension to counter this.
Upgrade do it do it....you won't regret it
I run 17" Bridgestone RE050 at 37 psi - I found 39 psi too harsh.
I run at 38psi and they are perfect!

You will not regret the choice to upgrade you handling. Driving an Alfa with poor handling is like having a boat that don't float or a plane that won't fly.. :)
or a train that don't - sorry that one doesn't work:)

David P: may i ask what suspension mods you have made?
check out my thread suspension upgrade and powerflex th rears, i have all my parts sources and costs as well save you all the hard work:)
 
#11 · (Edited)
Haha, perfect thread! Was just about to ask the same thing. When I got the wheels from Dougie the pressure was 2,7 in all tires and they felt great! Tried lowering to 2,3 but the steering was more sluggish and the ride not as sure-footed. 2,7 it is again!:thumbs:

And the tires were prefectly worn btw with the 2,7...

Julian: My 166 is absolutely rigid up to 150mph. Absolutely different car to the one I bought originally. You will not regret the choice to upgrade you handling. Driving an Alfa with poor handling is like having a boat that don't float or a plane that won't fly.. :)
 
#17 ·
It's probably the same as TeamAlfa´s. I've got Bilstein B8s, Eibach ProKit30, PowerFlexed rear axle and new "merc" bearings. Also rebushed the antiroll bar. Also lots of time on the wheel alignment computer to find suitable angles for the wheels. Now it's like stated, rock-steady up to top speed. Was averaging (is that a word?) 130mph yesterday at night at the freeway for 30min. After a little while this speed feels like 50 in my car. It's that good.

It might cost a bit, but the car sure is worth it! It is now, like someone said, the thinking man´s QuattroPorte.. :D
 
#13 ·
Yeah, as David says I ran them at 2.7. I run the 235/40/18s on the Ti at 2.7 also - As the book says.
 
#15 ·
Wallowy ride is definitely due to excessive tyre pressure..
It's like you're riding on balloons..Don't forget pressure rises with heat..
So if u have 39 psi cold, it can easily go to 45 when hot..Max pressure
in 225/45's is 54 psi..So you're awfully close to max pressure..
This is why , here in Lebanon with the heat, tyre shops advise
to put 32 psi cold..Ride is perfect, even though steering is a bit harder
but not that much...And no , wear is even :thumbs:
 
#16 ·
Handbook states 39psi at cold, so obviously expected to rise when in use!

What is your tyre wear like at 32?
 
#18 ·
Dougie, tyre wear is fine at 32..I've only driven the car 2500 kms so far, but I see no uneven wear on all fours and the car surely feels more planted with 32 psi..I could'nt drive it with 39 for 1 hour..It was too stiff and bouncy and felt like it could slide on water...I guess the quality of roads here has something to do with it..:thumbs:
I drive a GMC Yukon with 275/70/16 tyres with only 35psi all round and no wear at all after 9 months of use...I think under pressurising
is up to us and road and weather conditions..It will not affect the tyres if balancing and steering are all OK..:thumbs:
 
#19 ·
I run mine at 35Psi all the time and bump it up to 39Psi only when i have 4 or 5 people in the car. She runs like a dream at 35psi, with even tyre wear all round. At 39Psi and without a full load she seems a bit jittery in the corners. The book says 2.3 - 2.7 bar.

Now using google conversion factor of 1 bar = 14.5037738 pounds per square inch, 2.3 bar is 33.36Psi and 2.7 bar is 39.16Psi. I suggest 35Psi for daily driving and with the family in and a full load 39Psi.

Cheers
 
#20 ·
Hi Stephen,I'll try to go with your suggestion and go with 35psi.
How is it like driving a 166 In Dubai ? They must be rare like hell there.
Any spare parts,and anyone can fix them ?
What's the retail price on a used 3.2 face lift model 2004 ?
Here in Lebanon they are very rare and I have not seen another one on the road for the last 2 months...Mind You.I saw last month alone : a 159 2.2 JTS,a GT coupe and a Brera.........
Plenty of 156's and 147's though :confused:
 
#24 ·
Haven't got the exact figures in front of me, but most important was that I tried to get the rear wheels as neutral as possible. Made big difference for the hi-speed stability from factory stated settings.
 
#25 ·
David,
I have also just spent a small fortune on a suspension rebuild, and I agree that it is definitely worth it, totally transforms the car.

For my wheel alignment, I used the settings listed under "166 sport" on the Corghi computer, which correspond to;
Front -2mm total toe
Rear +3mm total toe

This is also what the Alfaworkshop recommend, as opposed to the factory settings of
Front -4mm
Rear +5.5mm.

The stability is very good, and I believe the rear geometry is key to this.

By the way, do you have any thoughts on fitting new bushes to the front anti-roll bar?
 
#26 · (Edited)
Yup, sounds a bit like my settings, the factory specs really didn't do it for me. Too much rear toe for my liking. As you say, it's all in the rear geometry in my book also. Have tried some extreme settings to see how it affects the car and experimented a bit. But it's not a Porsche GT3, 166s are best as stable hi-speed cruisers, but with those settings you can also thrash through the roundabouts at full speed! I'm trying to get rid of some understeer though, but I think this can be minimized but tweaking here and there.

EDIT: Front end of my car is in very good shape, no need to refurb any major parts yet. So no bar rebush yet...
 
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