UKF Posted July 26, 2017 Report Share Posted July 26, 2017 Hi guys, So I had a set of my own BC racing coilovers on my ISF fitted by Blackboots and geo done at WIM back in January. They did transform the car in terms of handling, it went round corners like glue but after a while I was finding the ride too stiff and not really suited to the roads I was travelling. Decided to fit the OE springs mated to a set of Bilstein B6 dampers, done by a local garage. My rear tyres were down to there limits so a pair of Yokohama Advan V105s 255/35/19 were fitted at the same time. Geo was done after fitting see below. Problem I have now is the car pulls to the left, something I never noticed on the BC coilovers. My ride height now is about 1/2 inch higher all round then what it was on the coilovers. Looking at the geo below is there anything that stands out as to why the car would pull to the left more noticeably? If not, could the new rear tyres be causing the car the pull ? I've also added my geo done at wim after the coilovers were fitted as comparison although I was riding a little lower. WIM coilover Geo Quote Link to comment Share on other sites More sharing options...
UKF Posted July 26, 2017 Author Report Share Posted July 26, 2017 Looking at it, when I had the coilovers i had a lot more negative camber on the front right side -1.12 compared with the front left -0.59 Now I have more camber on the front left side -0.54 than the right -0.35. with the natural slope of the road left could this be causing the more noticeable left pull ? Toe both front and rear seem relatively unchanged Quote Link to comment Share on other sites More sharing options...
Tony Posted July 27, 2017 Report Share Posted July 27, 2017 The camber change is unremarkable, even a change in the fuel load can account for that but once again i'm disappointed the castor wasn't measured and without that i can't comment on the pull.... The castor has many duties but it's main one is directional stability. Quote Link to comment Share on other sites More sharing options...
UKF Posted July 27, 2017 Author Report Share Posted July 27, 2017 Yes I was suprised when the guy told me they don't measure it. Can't remember the reason why but it was a Hunter machine. Regarding the castor angle, would you expect that to change when changing shock absorbers? The actual shock position can't change as it's mounting points are fixed. Or am I missing something? Quote Link to comment Share on other sites More sharing options...
Tony Posted July 27, 2017 Report Share Posted July 27, 2017 Well it shouldn't move but we need to know for sure since a castor change would make the car pull.... Them saying they don't measure it is utter bollox. I think the real reason is it's a hard angle to understand or explain to the customer. If i were you i would go back an point out you paid for a "full geometry" which includes the castor and yes the machine can measure it. Or even better give me your name and registration and I'll contact them for you 1 Quote Link to comment Share on other sites More sharing options...
UKF Posted July 27, 2017 Author Report Share Posted July 27, 2017 Haha yes that would be an interesting conversation ! I'm just going to have a trip down to WIM and get it checked out properly next month. Quote Link to comment Share on other sites More sharing options...
Tony Posted July 28, 2017 Report Share Posted July 28, 2017 Since they have limited adjustments the fee will be miniscule or it will be just a chassis image and diagnostics so again a token fee. Quote Link to comment Share on other sites More sharing options...
UKF Posted July 31, 2017 Author Report Share Posted July 31, 2017 Cheers Tony, did a few more miles in the ISF this weekend, had a trip to IKEA in Bristol joy of joys! Anyway something is definitely not right, not only does the car want to go left all the time, at motorway speeds 70-80mph the car felt that it didn't want to go in a straight line. Best way i can describe the feeling is driving in a very strong crosswind however there was no wind outside of note. Car didn't feel confident at all. Another thing I noticed was in the car park when doing a left turn the steering wheel wasn't too keen at finding centre again, it seemed fine when doing a right turn. I definitely think this is something to do with the shock install, I cant hear anything loose or any knocking so I don't think its ball joints or track rods. I have been doing a bit of reading and apparently the top mounts need to be installed on the new shock in a particular way. I have read that there are arrows marked on the top mount that need to face in a particular direction? I have no idea which direction they should face but if incorrectly mounted it can affect caster settings. I deffo need to get my caster readings done as a starting point, if they are out I will go back to the garage that installed them and get them to check but I cant find anywhere on the internet which direction the arrows on the top mounts should face for the Lexus ISF? Have asked the question on one of the US forums so lets see if I get anything back. I'm guessing you cant see the arrows once the shock has been mounted? will have a look tomorrow from the engine bay. If I can, then my friend has the same car so can get him to check his otherwise it involves taking the strut off again. Arrrgh! Quote Link to comment Share on other sites More sharing options...
UKF Posted August 1, 2017 Author Report Share Posted August 1, 2017 Looks like there is a correct orientation to the top mounts according to the Haynes Manual: http://workshop-manuals.com/lexus/is_f/v8-5.0l_(2ur-gse)/steering_and_suspension/suspension/suspension_strut/shock_absorber/component_information/service_and_repair/front_shock_absorber/page_6425/ Had a look at mine and th marks are not facing as in the diagram above. Tony have you seen this before regarding top mounts? Could this be the cause of my left drift? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 1, 2017 Report Share Posted August 1, 2017 Yes, on some cars rotating the top mount can adjust the castor but in most cases it also adjusts the camber meaning there is an optimum position. The adjustment only works if the damper is not central in the mount. Quote Link to comment Share on other sites More sharing options...
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