Bimota Forum

[bimotabob]

Hey i need some technical support from the experts on here.

I'm serious about changing my Furano rims, look great but very heavy.
Heard its the best mod on these to go for light weight rims.
No carbon fibre is not an option for several reasons and cost is not at the top of the list. Aluminium cast or forged for me - no magnesium.
Money is not a major concern due to the rim width itself and as i'm changing both this wont be cheap anyway so it's not part of the discussion.
Obviously 6 inch is more available these days second hand but i can still get a light weight 5.5 rear rim so availability is not part of the discussion.

So i think there's 2 options:

1) Stay with current 5.5 inch.
2) Change to 6 inch.

So we need to consider the implications on:

1) Handling - same, better or worse
2) Tyre availability
3) Swing clearance
4) Chain related clearances.

Handling is most important. if it makes it worse i wont do it.
But it's not a tangible thing to me to know.
Could anyone give a experience based idea on what to expect?
Why has there been a push for 6 inch rims - is it handling, looks or traction?

Tyre availability is a lesser factor but i'm told 190 width tyres for 6 inch are standard on many bikes so they are common and will stay that way.
However this is a road bike so no slicks so I'm interested in what people think about ongoing availability of 180/55-17 sports road tyres please.


Swinging arm and chain issues is certainly something to consider.

Chain clearance to tyre: 7mm
180/55-17 Tyre to swingarm each side: 10mm (has more in front on tyre)
Chain clearance to frame: 2mm (so cannot move chain away from tyre)

Looks to me like its possible but i know tyre width is a standard not an actual size. i.e i'm running a Michelin Pilot Power but another brand may be less or more than my tyre.
A point of note though, i'm running 530 RK XW O-ring and very keen to change to 525 so clearance to frame will change.
Basically i'm running probably the wider chain it would ever run now.
Anyone changed their YB series to 525? 520 is not an option for me.

I have a feeling that some Furano models may have had a 6 inch rim fitted from Bimota but no proof of this.
Maybe someone has fitted a 6 inch rim to their YB8 or YB10 already?

Be interesting to hear thoughts on this as buying time is getting near as my long term savings is ready

Kind regards
BB
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YB8EI

[2bims]

Theres a lot of info on the Forum re wheel weights if you use the "search" facility for wheel weights....

http://www.bimotaforum.co.uk/viewtopic.php?t=1655&postdays=0&postorder=asc&start=0

Weighed a few different makes of wheels recently and thought someone may be interested in the results so far.
All same size wheels, diameter and rim width, and all without disc's but with bearings etc and sprocket on the rear.

Antera ...................................Front 6kg Rear 8.95kg
BST carbon.............................Front 2.95kg Rear 5 kg
Dymag 7 spoke forged alloy.....Front 3.45kg rear 5.9kg
Dymag carbon........................Front 2.75kg rear 4.75kg.

I know that the Oscom Bimota rims are a lot lighter also than the anteras...saving 5-6Kilos per wheel swap.....

I dont think theres an issue re ongoing availability of 180 tyres....Bimotas Db5,6,7 and a lot of Ducatis still use 180's as a standard....wider tyres means slower turn in so not always the best....

One of the main things to check is Brake disc fitment, and speedo drive.....if you are wanting to retain the same brake discs...otherwise it could be a signigicant extra cost in either new discs and or brackets/plates etc....

Evidently spacers and spindles would also need to be matched or manufactured

I'd agree that maybe the extra cost or fragility of magnesium or carbon wheels over alloy isnt necessary as only minor weight savings can be accrued as a result

I'm sure theres a weight comparison of Oscom wheels on here somewhere also but cant find it at present...although I know they are some 5-6kilos lighter than the anteras (albeit your anteras are slightly different with the rivetted rims to the spokes)

[Evilchicken0]

If money isn't a major concern then try to contact a wheel manufacturer. Dymag is easy for us in the UK but may have a more local company. Buying a second hand pair might seem good value but you want them to match so the front has to suit the brake carrier bolts - these might be Ducati / Yamaha 6 bolts then the hub needs to be wide enough and you may need a pair of carrier spacers ... so really a new pair are a lot easier and you can choose the colour too.

Stick to a 5.5 the bigger rim and tyres are good if your putting out a lot of power 170 hp or more
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Don't read everything you believe

[Jonny B Bad]

I agree with Chuckie - nothing to be gained by going to a 6 inch rear unless the bike's knocking out current bike levels of power and certainly not worth wrestling with clearance issues to get anything bigger than a 180 tyre on the back.

Lighter wheels do make a massive difference to the feel of the bike - in the areas of acceleration, braking and turn-in and it just feels like a lighter bike to ride. Clearly the benefit is all the greater if you're shedding particularly heavy original wheels.

Dymag list for a Furano - and produce a good product.
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What, Jonny's gone!

[vort28]

Hi BB

Not sure of the weight of your wheels, but are'nt they the split rim Marvics with Magnesium spokes and alloy rims?
On the 6 or 5.5 rim , all depends on the tyre size. I see no reason to go wider than the 180, so that is your widest measurement not the rim !!!
So 5.5 or 6 will make no different to the clearance.
Different manufactures recommend different rims for 180 section tyres, Pirelli say 5.5/6 but Michelin say 6.
I run Michelins mainly and have changed my sb6/db4 and vdue from 5.5 to 6 inch rims. This was because of the availability of the 6 inch rim .
Have noticed no difference in handling .
Previously on my DB4 I had Pirelli corsa tyres as thats what it came with and thought it handled OK , rode it back to back with a db4 with Michelins pilot powers and replaced the Pirelli's that weekend. Thus I have noticed tyres made more of a difference on the handling than rim width ( This was before I put 6 inch rim on the 4).
Go for alloy forged wheels, best all round , money/weight etc.

[2bims]

Strange that...i put pirelli corses on my db2 based on a recommendation... Then when i got the db4 with michelin 2ct compounds i preferred those for the profile....and then put them on the db2, db5, db6 and the vdue...happy all round with them and all 180 rears...

[vort28]

[2bims]

Oh yeah...i remember who recommended them now...cheers....well..
At least you ended up with my yb11 shod with pirellis..

[bimotabob]

I have been looking Dymag as they do an exact set for the Furano which will drop in apparently.
They offer the rear in 5.5 or 6 inch.

Otherwise i get the dramas mentioned like sprocket and disc mounting issues and clearance factors if i get a jap donor set of rims.

Interesting hearing that at least one manufacturer recommends 180 rear tyre for 6 inch rim fitment, that was a nice surprise. If i could go 6 inch and still run the 180 tyre with good handling that would be awesome as i believe i wouldn't have clearance issues to concern me.

The Furano has BBS hubs and spokes, they come apart into pieces and the Akront rim gets easily removed also but its too heavy for magnesium.

Thanks for opinions and information.
Hearing other rim weights gives perspective.
Just found some info i wrote down on my rims for comparison:

Front wheel:

Akront Rim: 2876gm
L/H Hub Cover 626gm
R/H Hub Cover 618gm
Hub 2106gm
Discs (each) 1568gm
Hub spacer 34gm

Rear wheel:

Akront rim 2740gm
L/H Hub 1528gm
R/H Hub 1092gm
Hub 2440gm
Disc 1010gm
Hub spacer 76gm
Sprocket (Al 530-46) & Carrier 1498gm

Something like:
Rear Wheel: hub parts and rim 9374gm
- no fasteners at all or disc but including sprocket and carrier assy.

Front wheel: assembled hub plus rim 6446gm
- no rim fasteners or discs


So savings wise there could be close to 10kg as add fasteners and aluminium valve stems to those figures mind you.

HEAVY HEAVY HEAVY

I like the idea of reducing the bikes mass from 190kg to 180kg (all fluids except fuel)
Unsprung weight too
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YB8EI

[Evilchicken0]

180 size tyres can be a bit misleading, a 180 can be as "wide" as a 190 depending on the height ratio
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Don't read everything you believe

[vort28]

I have dymags on my DB4/SB6/vdue, one of the reasons I went for them was the ease of fitment. They list most Bimota's and if you talk to them there is usually a deal to be done.
Forge alloys I weighed were not that much heavier than the carbon, and that was the older forged alloys , they now machine a bit extra out at the base of the spokes so will be slightly lighter.
See this post .
http://www.bimotaforum.co.uk/viewtopic.php?t=3913&postdays=0&postorder=asc&highlight=wheel+wieght&start=0


Wow those wheels are VERY HEAVY !!!! even heavier than the Antera's!!!! I think I have some weights with tyres etc somewhere if you are interested.

[bimotabob]

Yeah heavier than Antera rims, maybe heaviest rims on a Bimota ever!

The Dymag price brought tears to my eyes as our local agent gave me the numbers a few months back.

Do like the look of those new forged rims, they look quite light with the spoke relief for sure.
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YB8EI

[Bud977]

I've got R1 wheels with a 6.0" rear in my YB8 race bike so it all fits.

There is clearance even for a 200 tyre. I'd prefer to run a 180 or 190 but they didn't have those slicks in stock at the last race meeting so I ended up with the 200. The centre of the tyre is within 10mm of the swingarm but doesn't even rub when it grows at speed.

The only problem was with the hugger. The wheel wouldn't turn once I stopped. The hot rubber coming off the edge of the tyre was sticking the tyre to the hugger when stopped. So I took the hugger off.

I didn't notice any difference in handling with the bigger 200 tyre.

The R1 wheels are a great alternative as they are light, readily available and some have 320mm discs as per the standard Brembos. They are certainly not a drop in fit though. You have to machine the sprocket carrier and disc mounting surface on the rear, make axle spacers, caliper brackets and recess the mounting bolts for the front. I did it myself in my own workshop, apart from machining the disc mounting surface as the wheel is too big to fit in my lathe.

[Bud977]

I have a 520 chain set up on the YB8. Regardless of the chain size you run, the inside face of the sprocket remains in the same place so the chain to tyre clearance is approximately the same.

The clearance changes with the bulk of the chain. A chain with thinner side plates and thinner O rings would have better clearance. Race chains tend to be less bulky as they are made of better material.

[bimotabob]

Thats interesting you can fit a 200 as i was worried about a 190.
I think all the YB8's have the same swingarm but not 100% sure.

Yeah R1 wheels are light alright, would be cheaper than buying new forged by maybe half the money after machining costs - if i was to find a set.

Options options

The rear hugger i forgot about, yeah that could be an issue on mine.

How close is your chain to tyre as mine is close with the 180?
The inside on yours should sit where mine is unless your front sprocket has a different offset but then the frame is so close its pretty close tolerance mods.
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