Thread: Ohlins knocking
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      04-10-2020, 04:30 AM   #89
David.m
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Drives: M2 LCI 6MT BSM
Join Date: Aug 2016
Location: Australia

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This might be of interest to anyone with the dull knock at very low speed. I installed my Ohlins R&T a few days ago and straight away driving up my paved driveway (moderate incline) I had continual low volume knocking up front then some louder knocks as the front wheels went out onto the road (which I do carefully otherwise the car bottoms out). Reversing back down the drive I had the same knocking, driving forwards down the drive no knocking. Also no knocking driving on road, over speed bumps nor any issues on smooth concrete carpark surface. Problem seemed to be a combination of low speed, small undulations on road surface and low compression on suspension.

Anyway after a bit of stuffing around I discovered the cause of my knocking was slight movement of the springs when the top hats are rotating. With the wheels off, turning lock to lock there was a knock noise from the left spring every time it turned through the same spot. Using my hand I applied some side force to the spring as I pulled/pushed the steering through a full lock to lock. The spring noise was now gone. Wheels back on and driving up the driveway no knocking but did have a couple of very faint knocks as wheels went over onto road, but now very quiet compared to what they had been, hard to tell if it's left/right or both. If there is no further change in the next week or so I'll try moving the right spring while turning steering through it's range.

This probably explains why the oem springs have the big rubber seats at each end and the recess to hold the spring end. The flat ended Ohlins springs sitting on a flat plastic/rubber seat might be prone to slight movement at low compression until they settle into 'their' position. Another fix might be to increase pre-load but the downside of that I think would be a firmer spring rate at it's initial compression point.
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