Suspension question regarding shock spring and weight

This is for my '07 Daytona 675 and not an SV.

I've previously seen a video about the rear spring being for a much heavier weight on my bike than is required and I've been thinking about it.

After reading on here a bit I found the Race Tech spring calculator. I've entered the weights as required for my bike (185kg half wet, 89kg person without gear) and the front springs come out bang on. I have worked out however that the rear is WAY oversprung by about 71kg!

This may seem like a stupid question but should I be looking at changing to a better spring considering it's reasonable money to do so? I do like the odd trackday and am at slow inters pace at the moment. I will also be using the bike for occasional trips and occasional two up although I have another bike for this. If I do go down the spring changing route would I be wise to get a slightly stiffer one to account for the track days and occasional extra weight?

Thanking you kindly.

[TSM]

naa that is wrong

Originally Posted by monkey

This is for my '07 Daytona 675 and not an SV.

I've previously seen a video about the rear spring being for a much heavier weight on my bike than is required and I've been thinking about it.

After reading on here a bit I found the Race Tech spring calculator. I've entered the weights as required for my bike (185kg half wet, 89kg person without gear) and the front springs come out bang on. I have worked out however that the rear is WAY oversprung by about 71kg!

This may seem like a stupid question but should I be looking at changing to a better spring considering it's reasonable money to do so? I do like the odd trackday and am at slow inters pace at the moment. I will also be using the bike for occasional trips and occasional two up although I have another bike for this. If I do go down the spring changing route would I be wise to get a slightly stiffer one to account for the track days and occasional extra weight?

Thanking you kindly.

I have my rear sprung for my weight (~80kg without gear), though while it was still a road bike, I did occasionally carry a pillion and it felt like crap. Increasing the preload helped, but at the end of the day, if you have a precise track-biased rear setup, it isn't going to work when you almost double the weight (depending on how partial the missus is to pies ) from someone hopping on the rear!

I guess the compromise is to spring the shock so that you can achieve correct rider sag with the minimum amount of preload you can get away with and then work out how much to add when you take a pillion. This is easy if you have a remote preload adjuster, but will suck and skin your knuckles if you have to get out a C spanner each time!

I personally would set it up so it is correct for you and use the other bike if you need to take a pillion!

That's what I'm thinking. Does the calculator look correct to you? Just reading on the other forum about it but that site's confusing for the simplest thing.

Originally Posted by monkey

That's what I'm thinking. Does the calculator look correct to you? Just reading on the other forum about it but that site's confusing for the simplest thing.

Yeah - Just had a quick play - Looks about right. the stock 675 shock is quite oversprung by single rider standards, but then it works with a pillion! Thing is - Triumph only supply one shock with their bikes and so they can only set it up one way. Despite what the 675 site say, it's not "wrong", just very road biased.

You mean track biased?

I'm just back from an excellent European road trip (French Alps) and I had to take the old Ninja for the comfort but on a lot of the roads I was wishing I had the Daytona. I need to sort out the footpeg position for longer stints on the road (my knees are dodgy) but I'd like to sort out the suspension too.

Do you think the spring for a 120kg or so rider weight would make much of a difference accounting for luggage on a trip/trackdays/pillion (with pre-load adjustment)?

Originally Posted by monkey

You mean track biased?

I'm just back from an excellent European road trip (French Alps) and I had to take the old Ninja for the comfort but on a lot of the roads I was wishing I had the Daytona. I need to sort out the footpeg position for longer stints on the road (my knees are dodgy) but I'd like to sort out the suspension too.

Do you think the spring for a 120kg or so rider weight would make much of a difference accounting for luggage on a trip/trackdays/pillion (with pre-load adjustment)?

No- road biased as in 2-up riding etc. People think - firm spring = track, but that is not necessarily the case. You want a firm setup, but one that is going to give as much feedback back as possible. The shock regulates how much the damper can move for a given weight applied and if it is way over-sprung, then ultimately you'll use less stroke which will give you less feedback and also reduces the ability to track the road

My take on suspension is unless you are chasing laptimes times, there is a quite a wide latitude in adjustment that people will find acceptable. After a point, unless you a running the same corners again and again, you won't be able to differentiate between a click more compression, or 1mm less preload etc.

A lot of people might chime in and disagree on that point, but I think a rider needs to be able to put in consistent laptimes (something quantifiable), before committing too much time to suspension setup. Otherwise there are too many variables for it to be objective.

Bottom line - I think the main thing is to set the bike up for your weight i.e set correct rider sag using preload and re-spring if necessary.

As for you situation... I honestly couldn't tell you what you would prefer! You can sit down an do some maths or use the racetech calculator (though I don't understand how it differentiates between sprung and unsprung mass with the bike weight?). I wouldn't worry too much about luggage - that'll only be 10kgs or so. It's having a pillion that adds a lot of weight.

-or-

I would talk to a suspension place and see what they would advise as I don't really know what the starting point is for track + luggage + pillion riding! You might find it isn't too far off the stock shock! Be worth getting some proper advice (rather than my ramblings) before dropping the cash