Saab 9-5 front wheel spacers

Saab 9-5 front wheel spacers

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McVities

Original Poster:

354 posts

197 months

Saturday 17th November 2018
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I am looking to upgrade the front brakes on my Saab 9-5 Aero, to this end I have some 345mm discs and the calipers from a Vectra VXR which handily bolt on.
The snag is that a test fit shows my wheels won't clear the calipers. I would be looking to fit some hub centric wheel spacers to give a little extra room. I plan to keep the increase to as small as possible, but it looks like around 10mm per side will be required.

The car is lowered on a set of springs from Abbott racing which are paired with Bilstein B8 dampers. There is a strut brace and the subframe, wishbone and anti roll bar bushes have been replaced with polyurethane.

Any thoughts on how the spacers would affect the handling and grip? The turn in is currently pretty good and understeer is only a problem if I am careless with the throttle on tight bends.

GreenV8S

30,150 posts

283 months

Saturday 17th November 2018
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McVities said:
I am looking to upgrade the front brakes on my Saab 9-5 Aero
What problem are you trying to solve?
McVities said:
to this end I have some 345mm discs and the calipers from a Vectra VXR which handily bolt on.
Have you calculated what effect this is going to have on the brake balance?
McVities said:
The snag is that a test fit shows my wheels won't clear the calipers. I would be looking to fit some hub centric wheel spacers to give a little extra room. I plan to keep the increase to as small as possible, but it looks like around 10mm per side will be required.
That's pretty thin for a hub centric spacer. How tall is the locating ring?

McVities said:
Any thoughts on how the spacers would affect the handling and grip? The turn in is currently pretty good and understeer is only a problem if I am careless with the throttle on tight bends.
It won't do it any favors. You'll get more kick-back and tram lining and more bearing wear, although for 10mm I wouldn't expect any of these effects to be huge. Do you have enough clearance in the wheel arch through the whole range of suspension and steering positions?

Tony1963

4,699 posts

161 months

Saturday 17th November 2018
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OP,

As above, why are you fitting larger brakes? What was the problem?

And have you tried to source larger wheels? Yours, with tyres on, will have value against the change.

Tony1963

4,699 posts

161 months

Sunday 18th November 2018
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I just love threads where the op disappears frown

McVities

Original Poster:

354 posts

197 months

Sunday 18th November 2018
quotequote all
GreenV8S said:
McVities said:
I am looking to upgrade the front brakes on my Saab 9-5 Aero
What problem are you trying to solve?


The standard brakes are not very confidence inspiring. They are 308mm vented discs with a single piston caliper, and after a few slows or stops they begin to fade quite markedly. The stopping power also feels a little lacking. This is not just me either, other owners have also reported that whilst for normal sedate driving the brakes are adequate, any kind of spirited driving leaves you in no doubt of the 1600kg+ mass of the car.
Within my car, the flexi lines are good and the fluid fresh, the pads are currently OEM equivalent pagids.
Yes I am aware that I could look at upgrading the pads, but that wouldn't cure everything. I have Goodyear Eagle F1 asymmetric tyres and whilst not supreme top rubber, they are reasonable, yet the current brakes will not lock up in the dry.

A little background info about the upgrade........

Hirsch, the factory approved Saab tuners (factory warranty retained) used to offer a 330mm floating disc with 4-pot calipers as an upgrade for the 9-5. This was eventually dropped in favour of the 345mm solid disc and single piston caliper. This was mainly due to the crossover pipe in the 4-pot caliper block being too close to hot bits and the brake fluid boiling within under extreme use. The single piston caliper doesn't suffer with this.
The official blurb reports the 345mm setup was chosen as it would continue to work with the existing ABS system as originally designed.
The 345mm system also found a home with the 9-3 Turbo X.
Careful cross referencing of the part numbers show that the parts of the Hirsch kit and that from the Vauxhall VXR are identical.


GreenV8S said:
McVities said:
to this end I have some 345mm discs and the calipers from a Vectra VXR which handily bolt on.
Have you calculated what effect this is going to have on the brake balance?

I hadn't, but as it was an approved upgrade, I hadn't felt the need to dig too deeply. The pistons used are larger than the existing ones and the pads larger too. This will provide a longer pedal travel but also proportionally more braking effort at the wheel. This will induce some weight transfer forward, so is likely to increase the braking effort further at the front and reduce that at the rear. This upgrade works with the ABS on existing springs and dampers, so I am not unduly concerned. I would like to hope that my firmer dampers and springs will reduce the amount of weight transfer under braking when compared with the softer OEM setup.


GreenV8S said:
McVities said:
The snag is that a test fit shows my wheels won't clear the calipers. I would be looking to fit some hub centric wheel spacers to give a little extra room. I plan to keep the increase to as small as possible, but it looks like around 10mm per side will be required.
That's pretty thin for a hub centric spacer. How tall is the locating ring?

That's a good question, I don't know and will have to check. A quick Google and it would seem the 10mm Eibach spacers I had thought had a locating hub ring don't and I will need to opt for the 16mm set instead.

GreenV8S said:
McVities said:
Any thoughts on how the spacers would affect the handling and grip? The turn in is currently pretty good and understeer is only a problem if I am careless with the throttle on tight bends.
It won't do it any favors. You'll get more kick-back and tram lining and more bearing wear, although for 10mm I wouldn't expect any of these effects to be huge. Do you have enough clearance in the wheel arch through the whole range of suspension and steering positions?
Ah ha, thank you. This is what I was looking for. A little extra tramlining and kickback I can live with. I have looked at the arches (first thing I did) and with the existing wheels I have, there is plenty of room to go wider at all lock positions and for the range of vertical wheel movement.

McVities

Original Poster:

354 posts

197 months

Sunday 18th November 2018
quotequote all
Tony1963 said:
And have you tried to source larger wheels? Yours, with tyres on, will have value against the change.
I currently have a set of 17" wheels on which I feel provide a happy medium between handling and comfort. Going bigger would make for a harsher ride, add to the risk of pot hole damage and add extra cost to the tyres. As an aside, I also like the look of the wheels as they are, this however is the lowest priority.

McVities

Original Poster:

354 posts

197 months

Sunday 18th November 2018
quotequote all
Tony1963 said:
I just love threads where the op disappears frown
I haven't wavey just had life things to do rather than be on the internet.

Tony1963

4,699 posts

161 months

Sunday 18th November 2018
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smile

Tony1963

4,699 posts

161 months

Sunday 18th November 2018
quotequote all
In that case, just give the spacers a go, you haven’t much to lose.

Great car, by the way.

GreenV8S

30,150 posts

283 months

Monday 19th November 2018
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McVities said:
the current brakes will not lock up in the dry.
You've got ABS. That's why the brakes won't lock in the dry. If they won't apply enough braking to engage the ABS then they are faulty and you should fix that before considering an upgrade.

McVities said:
The pistons used are larger than the existing ones and the pads larger too. This will provide a longer pedal travel but also proportionally more braking effort at the wheel. This will induce some weight transfer forward, so is likely to increase the braking effort further at the front and reduce that at the rear. This upgrade works with the ABS on existing springs and dampers, so I am not unduly concerned. I would like to hope that my firmer dampers and springs will reduce the amount of weight transfer under braking when compared with the softer OEM setup.
The steady state weight transfer under braking is determined by the wheelbase, height of the center gravity and the total amount of braking, and nothing else. If the old brakes were in good working order then peak braking effort will be determined by the tyres and the road, and nothing you're doing here will change that.

The original brake balance was probably about right. Mainstream production companies tend to be pretty good at getting that sort of thing right. It sounds as if the new brakes will change the balance, which means it will now be wrong. You could easily calculate the change in hydraulic and mechanical leverage to work out how much it will be wrong by. If it is only a small amount I wouldn't panic over it, and in any case the ABS will hide a lot of sins, but personally I would think carefully before relying on the ABS to compensate for a wrongly balanced brake system.

Are your insurers OK with the proposed modification? Sometimes they can get a bit funny about people modifying safety critical parts of the car.

McVities

Original Poster:

354 posts

197 months

Friday 3rd May 2019
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To come back and update this......

I got hold of some 16mm hub centric spacers and longer wheel bolts.
Initially the steering felt a little heavier at parking speeds but no different once on the move. The turn in feels slightly sharper but there has been no change to the front/rear balance in terms of under or oversteer.
There has been a slight increase in torque steer when at full throttle in 2nd, however 3rd still has the same decent manners as before.

This did allow just enough space to squeeze the 345mm setup behind, and as the hard lines under the car needed replacing, it seemed a good a time as any to have the brakes and Hel stainless braided flexi's fitted.
Currently still running them gently while the pads bed in but initial feedback suggest as would be expected - less pedal pressure required for the same deceleration but needs a smidge more travel to achieve. Made modulation a tad easier.
All in all very happy and looking forward to giving them a good pasting.



GreenV8S said:
McVities said:
the current brakes will not lock up in the dry.
You've got ABS. That's why the brakes won't lock in the dry. If they won't apply enough braking to engage the ABS then they are faulty and you should fix that before considering an upgrade.

Maybe I should elaborate a bit....... Jumping on the pedal like a neanderthal would cause the abs to come in, but starting with medium pressure and building to foot to the floor would not, hence I feel the brakes can do more.
The existing setup would also fade quite rapidly, and this is the primary reason for the bigger brakes.



GreenV8S said:
McVities said:
The pistons used are larger than the existing ones and the pads larger too. This will provide a longer pedal travel but also proportionally more braking effort at the wheel. This will induce some weight transfer forward, so is likely to increase the braking effort further at the front and reduce that at the rear. This upgrade works with the ABS on existing springs and dampers, so I am not unduly concerned. I would like to hope that my firmer dampers and springs will reduce the amount of weight transfer under braking when compared with the softer OEM setup.
The steady state weight transfer under braking is determined by the wheelbase, height of the center gravity and the total amount of braking, and nothing else. If the old brakes were in good working order then peak braking effort will be determined by the tyres and the road, and nothing you're doing here will change that.

The original brake balance was probably about right. Mainstream production companies tend to be pretty good at getting that sort of thing right. It sounds as if the new brakes will change the balance, which means it will now be wrong. You could easily calculate the change in hydraulic and mechanical leverage to work out how much it will be wrong by. If it is only a small amount I wouldn't panic over it, and in any case the ABS will hide a lot of sins, but personally I would think carefully before relying on the ABS to compensate for a wrongly balanced brake system.

The upgrade was specified and designed by the engineers at Hirsch, and then given Saab factory approval and retention of OEM warranty (I believe it is also TüV approved). Whilst the balance under heavy braking may be altered, some very clever people are more than happy with it.....so I am not unduly concerned.



GreenV8S said:
Are your insurers OK with the proposed modification? Sometimes they can get a bit funny about people modifying safety critical parts of the car.
Yup, the upgrade did attract a small increase in premium as would a pad upgrade. They were happy with the provenance of the system and that it was installed by my local independent garage.

Edited by McVities on Friday 3rd May 11:50

TheTardis

214 posts

189 months

Sunday 11th August 2019
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So how are the brakes now...?

McVities

Original Poster:

354 posts

197 months

Monday 19th August 2019
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Absolutely wonderful.
Consistent and repeatable stopping power.
A very distinct improvement on the original setup.