# Twitchy stearing on Seiran 24



## GuyY (26 May 2010)

My Seiran 24 (Challenge) likes to straighten up repeatidly on gentle curves when light stearing pressure is applied. In a straight line it feels fine. On a moderate curve the stearing feels steady. But on a very gentle curve, e.g., coming out of a roundabout when your riding path switches curve direction, the stearing feels will suddenly "correct" the direction of travel into a straight line if your not firm with the pressure on the stearing. This effect is very disconcerting, especially when you're indicating with your hands and is particularly noticeable at light stearig pressure. There's a bit of slack in the stearing rod [in the joint component of the rod itself rather than the ball/socket joint parts] which is probably the culpret. Anyone else experienced this fault/characteristic? Anyone had exerience of 'tweeking' the stearing rod arrangement [and not ended up in a hedge!] on one of these things: what should I look for, touch, don't touch, etc.?


----------



## Fiona N (27 May 2010)

Are you sure it's not just a problem in the steering/headset bearings. It sounds exactly like the problem you get on an upright when the bearing race gets a bit uneven and the balls like to fall into the hollows. 

Of course, I'm not totally _au fait _with Seiran equipment but it might be worth checking the obvious before tinkering with the steering geometry.


----------



## Riding in Circles (27 May 2010)

If you have slack in the steering rod then you can do nothing until you have cured that, then check the head bearings are seated properly.


----------



## arallsopp (27 May 2010)

When you're stationery, can you move the bars without detecting a corresponding deflection in the wheel? Likewise, can you rock the bars clockwise/anticlockwise at all? (imagine they're the wings of an aircraft and the boom is the fuselage. Can you raise a wingtip?)

On my Furai (also a challenge) the front wheel has a tendency to throw crud at the steering bearings, which kills them pretty sharpish. The resulting play means that the front wheel will move independently of the steering (we're talking max 1 degree here) and that can be odd around cambers, quick S bends, stone chippings, etc).

When I replace them, I'll mount a bit of something to deflect the spray from doing it again.


----------



## GuyY (27 May 2010)

I'm fairly happy that the bearings are OK (only had the bike since the end of March...so famous last words). In terms of crud thrown at the bearings, the Seiran came with mudguards which sit tight over the tires so they should be providing sufficient protection from crud. The only definite observation I've detected is a slight movement between the ball/socket fitting and the main stearing rod. The ball/sockets are tight (for now) but where the ball/socket inserts into the main shaft of the rod, I see 'slack movement' of about 1-2mm(could be 2-3mm). I think(?) I'm surprised by the apparant relationship between the degree of movement in the rod compared to the change in wheel angle. I'll do a more thorough investigation when I get home tonight (kids allowing) and keep you updated.


----------



## GuyY (27 May 2010)

The play in the steering rod is about 2mm which is OK. But I think the engineering design used to connect the front fork to the handlebars (USS design) is an issue. If I plot the effort needed to turn the front wheel from 10 through to 2 (with 12 as straight ahead) I have two peaks of effort close to and either side of the 12 position. Leading up to these peaks the increase in effort is gradual before suddenly falling away to almost nothing next to the 12 position. This is when the stearing suddenly goes light and twitchy, as if something is loose. On the road, coming out of a roundabout the wheel could be tunred at an angle that sits it on the inner slope of one of these 'peaks'. So if I'm not concentrating the wheel 'drops' into this 'central zone' and the bike appears to suddenly run straight untill I re-correct it. When starting the turn I need enough curvature in my direction of travel to allow me to 'nudge' the stearing beyond these 'inner slopes'. I guess it's something I'll have to live with :-( ....otherwise the bike's really good fun !


----------



## Riding in Circles (27 May 2010)

Sounds odd, are you sure the steering has been assembled correctly?


----------



## GuyY (28 May 2010)

All looks as it should. No slack anywhere other than the joint between stearing rod and the ball/socket end piece. When the bike is stationary the effect is more marked than when moving. The faster I go the less the effect is felt (or so it seems) due to forces induced by a spinning wheel (?), although the stearing is light when in a straight line. The tires are 47-507 which may amplify the effect compared to thinner tires perhaps? My instinct is to think that the geometry used in the stearing is creating this pattern of "effort" for the front fork. I'm not an engineer, either practical or academic, so I'm at a bit of a loss. I'll carry on checking everything I can on a regular basis and see if any physical changes match the effects.


----------



## arallsopp (28 May 2010)

Any chance of a photo of the undersides? Got a cruddy camera phone here, so will take some snaps of how mine looks. I'm thinking along the same lines as Catrike here. Could be my pics don't match yours at all.


----------



## arallsopp (28 May 2010)

TOP:






DETAIL:





FORK END:





BAR END:


----------



## ACW (28 May 2010)

from what you describe as the effort required to move the stearing it sounds like the head bearings to me, you get dents in the bearing race and it takes a bit of force to move the stearing to the straight ahead position then the balls fall into the dents in the race and it goes light, but then requires more force to move the stearing out of this position, i would disconect the stearing link arm and try moving the forks on there own, 
good luck


----------



## ACW (28 May 2010)

had another read at the posts and it definitely sounds like the head bearing, desire to run straight ahead is a classic example of this


----------



## arallsopp (28 May 2010)

ACW said:


> i would disconect the stearing link arm and try moving the forks on their own



That is an excellent idea.


----------



## GuyY (28 May 2010)

I'll load up some photo's tonight hopefully & disconnect stearing bar and re-check.


----------



## GuyY (29 May 2010)

I took the steering rod off as suggested and 'lo-and-behold' the variation in force needed to turn the front wheel is still there. In fact when moving the wheel by hand the variation in pressure is even more pronounced. If, as you guy's suggest, the bearings are indeed "shot" then I'm very disapointed with Challenge's build quality as I've only had the bike since 12th March riding approx. 650 miles on roads in that time. What next? Take it to a reputable local bike shop to get them to confirm (from a professional point of view) the nature of the problem and depending on their findings, chasing Challenge via London Recumbents? Other options?


----------



## GuyY (29 May 2010)

I've added some photo's in the "Album" section of this site if it's still of interest.


----------



## Fiona N (29 May 2010)

Well I did suggest this right at the start


----------



## GuyY (29 May 2010)

Fiona N. Indeed you did suggest it first and was proved right. So many thanks for your contribution as it added a contender to the list of possible causes and proved to be 'bang-on-the-money'. Now all I have to do is work out what to do next: repaired locally and leave it at that, or have a 'polite' word with Challenge ?


----------



## Riding in Circles (29 May 2010)

Your dealer is your first port of call, if it is a new bike then it is covered under the sale of goods act, a reputable dealer will sort out a problem like this but you must give them the opportunity to do so.


----------



## GuyY (30 May 2010)

Hi Cattrike, you've confirmed what I thought. And many thanks to all of you for your invaluable input in identifying the problem.


----------

