Author Topic: Mullet nomad mk 2 (26" rear -- 27.5" front)  (Read 1938 times)

E-wan

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Mullet nomad mk 2 (26" rear -- 27.5" front)
« on: May 07, 2024, 08:14:17 pm »
I have a Mk 2 nomad where I have replaced the standard fork with a fork design for a Mk3 Nomad

the new fork is about 15 mm shorter crown to axel length which, when used with two 26 inch wheels Will give a slightly steeper head tube and see tube angle than the originally intended geometry.


As the mk3 nomad fork is designed to also accept 27.5" wheels, I am considering mulleting the mk 2 nomad

Mullet bikes for those not familiar, have a larger front wheel than rear wheel
typically 29 inch front and 27.5 rear
although plenty of people have tried it with 27.5 front and 26 rear.

Given that the new fork has a shorter crown to axle length, it shouldn't have as much impact on the geometry as it would to do this with a different frame.
(Ever so, slightly slacker head tube and see tube angle than originally intended)

Has anyone tried this yet with the mk2 nomad?


I'm running 2.5 inch Surley extra teresterial tyres.

I have a few spare front wheels, so I'm planning to try both of 26 inch and 27.5 inch front wheel with the same tyre for initial comparison.

If it works, I could always use a slightly wider tire at the front and it opens up options to the wider range of tyres available in 27.5.

Ewan


PH

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #1 on: May 07, 2024, 09:42:25 pm »
If you have the wheels there's no harm in experimenting and seeing what works for you.  It isn't a lot of difference, less than a degree, I'm skeptical I'd notice it on the steering and it would mean getting the saddle back 5mm to compensate if that bothered you.  You could make the difference up with tyre sizes, 0.5" smaller on the front would do it.
Even for the current Nomad the supplied forks come in a variety of lengths, 20mm difference between the longest and shortest from memory.
« Last Edit: May 07, 2024, 09:45:26 pm by PH »

Andyb1

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #2 on: May 13, 2024, 08:58:15 pm »
I have been making my rigid bikes “mini-mullets’ for a few years now - 26” wheels at both ends but 1.5 tyre at the rear and 1.75 at the front.  My logic for this is that the front end hits bumps hard so a little more tyre thickness softens the ride, while the rear wheel gets pulled over the bump.   I have the front tyre 5psi softer than the rear as it carries less load.

Danneaux

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #3 on: May 14, 2024, 03:39:36 am »
Sheldon Brown, here...
https://www.sheldonbrown.com/tires.html#:~:text=Wider%20Front%2C%20Narrower%20Rear&text=A%20wider%20tire%20will%20generally,some%20wrist%20discomfort%20on%20occasion.
Quote
Quote
Wider Front, Narrower Rear
A wider front tire makes sense in many applications, however, when handling and ride comfort are considered. A wider tire will generally provide better cornering traction than a narrower one, assuming appropriate inflation pressure.
A wider tire also provides superior shock absorbency. I personally prefer a slightly wider tire in front, since I suffer from some wrist discomfort on occasion.

Best, Dan.

Andre Jute

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #4 on: May 14, 2024, 01:11:06 pm »
With all due respect to Sheldon and Dan, and to E-wan too, I'm not so sure a wider front tyre than the rear on a bicycle is the wisest thing to do on any bike but especially on a touring bicycle. Oh, it is probably all right for day rides on known roads, if not overdone, but a distant long loaded tour is bound to throw up more stressful conditions and events.

My reasoning starts with two immutable hard facts:

1. On a bicycle, which is inherently unstable -- scope the "bi" in the vehicle name, the roadholding and handling (handling is the capability to save yourself and your bike when it runs out of roadholding) must be provided for the conditions at the limit, which always lurk on strange roads -- by definition the case during distant tours. An example would be a fast downhill at dusk with a suddenly tightening curve with at the apex a pothole you never saw until you hit it.

2. There is nothing as safe as an understeering bicycle, and the more so on a touring bike whose rider will be on a strange road in perhaps unforeseen circumstances when he might be tired and his reflexes less than track-sharp. I've never even heard of a touring or utility bicycle by a designer so incompetent that he made it intrinsically oversteering. This is the reason why experienced tourers go to great lengths to achieve equal loading on the axles. This is also the reason lowrider luggage and fittings even exist -- to arrange the weight transfer couple to slope upwards to the rear of the bike, and for more esoteric reasons of bike stability in crosswinds where a rearward centre of aerodynamic pressure is absolutely essential. Note that a neutral-steering bike is a lethal object because you don't know which way it will break even in casual use when it meets a small extraneous input, never mind at the limit of adhesion. Even bikes with zero use outside the highest level of racing are not neutral-steering: they just have very much smaller margins of understeer,
 and none are designed to oversteer.

Your quality purpose-designed touring bike is thus likely to be as safe as can be imagined, the more so if it has a longish wheelbase, when fitted with two equally wide tyres inflated to the maker's recommendation for the load and it's distribution. It doesn't matter whether the designer is a brainiac or a craftsman following and refining time-hallowed practice: the point is that there is an agreed envelope the owner of the bike pierces at his own risk.

Just putting on fatter tyres at both ends than the bike was delivered with will already sharpen up the roadholding and steering through a bigger contact patch with the road, and the handling too, while at the same time distancing even further the likelihood that you will ever require the greater handling. Fatter tyres are faster and safer and more comfortable while at the same time making the bike feel more "sporting", contrary to cycling myth.

Putting a fatter tyre only on the back, all other things being equal, will on smooth roads cause less understeer or, in extreme cases dangerous neutral steer or lethal oversteer as the rear wheel with its greater traction tries to overtake the reluctant front wheel.

Putting a fatter tyre only on the front will tend to cause the front wheel to turn faster than the rear wheel and thus give the bike less understeer. (I know, counterintuitive that the fatter tyre on either end reduces design understeer, but tyres are the least rational part of a bicycle, or a car for that matter.) This, modestly done, could make an unloaded but intrinsically relatively heavy touring bike more responsive to steering inputs. Andy's point about the rear wheel being pulled by the front wheel applies. It won't work so well in loaded touring, which is generally weight-biased to the rear of the bike.

The safest tyre choice all round is what the designer intended before the cost accountants started work by fitting narrower tyres than the designer wanted: that is, to fit the fattest tyres the bike will take, same size front and rear and to inflate them to spec for the load and its distribution, and to let the design geometry keep you safe from "going bush" (actually, here in Ireland, into the ditch which lines both sides of the country lanes I love) or landing in front of oncoming traffic.







 



« Last Edit: May 20, 2024, 07:12:32 pm by Andre Jute »

E-wan

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #5 on: May 20, 2024, 01:56:30 pm »
Thanks for your thoughts

I wasn't really considering running different tire sizes, front and rear

I'm happy enough with the 26×2.5 Surley extra terrestrial front and rear tyre.


What I am considering is running different wheel sizes front and rear with the same tyre size
(there may be a slight difference in tyre profile as the internal diameter of the rim on the rear wheel is narrower)

What do you make of this description of the way the force vectors change with a larger font than rear wheel from mullet cycles
https://www.mulletcycles.com/mullet-bike-technology/

By running at 27.5 wheel at the front of the 26 inch wheel at the back the front axle will be about 10 mm higher than the rear axle.

Given that, I am running a different front fork which is 10 mm shorter than the one intended for the nomad mk2, running the 27.5 wheel Front and 26" back would return the frame geometry to its original intended angles, albeit with a different size front wheel.

Ewan

Andre Jute

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #6 on: May 20, 2024, 07:08:40 pm »
What do you make of this description of the way the force vectors change with a larger font than rear wheel from mullet cycles
https://www.mulletcycles.com/mullet-bike-technology/

These mullet guys are describing a bike specialised for a gravel road without either crosswinds or other traffic and no close ditches or berms either. It has nothing to do with touring bikes because they are trying to shift even more of the bike's weight onto the rear axle, which on a touring bike like your Nomad, if Andy Blance had done it, we'd ask if he was all right on the day. (Yeah, I know, Mr Blance wouldn't, he is too experienced; I'm making a dramatic illustration.)

For those who're already put off by this sort of theoretical discussion, you can discover where the mullet guys went wrong by searching in the link E-wan gives for the word hysteresis. You won't find it, because the mullet guys say nothing about it, but it is what makes the tyres of all other bikes, except only bikes on a loose surface like gravel, work so well. Hysteresis is technically defined as an effect lagging its cause, and describes the compound of the contact patch on the tyre resisting change of direction or any other input, nibbling itself into the changed state. Okay, now you don't need to read the rest, because you don't want to turn your touring bike into an awkward duckling under perfectly normal circumstances for a tourer (weight distribution, crosswinds, heavy traffic close by your bike), even dangerous if you go too far.

The mullet guys even tell us it is a pure marketing exercise:
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Bike Geometry is a standard of measure used to market how a bike is supposed to handle.

Remember when I pointed out that, regardless of what ERTRO permitted the clowns among the manufacturers to do for cost reasons, a "29-er" with rims less than 40% of tyre width across the rim beads was not, repeat not, a 29-er, but a fashion-victim's acceptance of his fate.

In the very next sentence, the mullet guys give away the game:
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However, geometry plays a very small part in how the bike’s tires contact & react to the ground while in motion.

This is goldtropchen slurry-grade manure. The geometry of the bike, and all its dynamic vectors and all its weight, and all the inputs by the cyclist, react only through those two contact patches. But the misleading statement goes with "marketing" if you want to sell something else. That they contradict themselves in the very next sentence is par for this sort of marketing guff, five bob each way, but is too late. They've already given away the game.

I can do the same analysis sentence by sentence but there's no point. I'll just pick one more lowlight:
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One major factor left out of traditional bike design is how the rear wheel turns & reacts with the terrain.
[my emphasis]

This is more prejudicial nonsense. How the rear wheel turns and reacts with the terrain is automatically arranged in the standard safety bicycle (whose distinctive feature in contrast with the penny-farthing is its two equal-size wheels) by hysteresis as described above, a valuable safety feature in that it automatically adds understeer. And also, I might add, on gravel or loose sand by the "terrain" shifting under the tyre, an analogue for hysteresis. The mullets substitute "scrub radius" but the effect is the same.

The mullets know exactly what I'm talking about, and tell us so when they mention "dirt bike geometry" and label the symmetrical bike (same size wheels and tyres) a "safety bike". It's apples and oranges -- and only the dirt bike will benefit from the mullet, and be a trailer queen if you live some distance on busy roads away from the dirt. Nothing to do with touring bikes.

If you're still with E-wan and me, try looking at the mullets' illustrations, which are pretty good conceptually, if you're planning a dirt bike. Again, nothing to do with touring bikes. But note that the steering vector of the rear wheel is faster on the mullet, which is less safe than on the safety bicycle.

WHY IS THE MULLET NOTHING TO DO WITH TOURING BIKES?
A touring bike, or a utility bike for that matter, needs first and foremost to protect the rider, which by definition means same size wheels and tyres (or very small differences in tyre diameters and/or widths) with understeering geometry. The touring and utility bike needs to be ridden on any road surface the cyclist might meet, which the safety bike does superbly well, especially if fitted with fat tyres. Finally, the touring and utility bike must be intrinsically safe in all its designed elements which, besides relaxed geometry, means a centre of aerodynamic pressure well back on the bike (and permanently behind the centre of gravity otherwise the bike will swap ends in a blink at the slightest crosswind--or suck you under a passing truck), and predictable in response which also means understeer which in turn requires a rising couple towards the rear for the centre of gravity.

I hope you won't think I'm a neanderthal luddite, E-wan. It's your bike; you do what you want. I put up these articles for information to everyone, but I'm not trying to persuade anyone of anything. In fact, I enjoy hearing about other people's experiments; the guys who're taking one for the team always get extra kudos from me. If you're doing it anyway, I for one would love to hear your impressions.
« Last Edit: May 21, 2024, 07:11:08 pm by Andre Jute »

E-wan

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #7 on: May 21, 2024, 06:30:39 pm »
Plenty to think about

For now, I've got 26-inch wheels front and back, but with a much wider rim on the front.

Velocity Dually 26”
https://www.velocityusa.com/product/rims/dually-559

This has a 39mm internal diameter compared to the Ryde Andra 30 which I think is 19 mm internal diameter on the rear.

It makes a noticeable difference to the tyre profile with more of the tread in contact at the front.
(it also lets me run tubeless at the front with pepi tire noodle, insert so that when I'm not carrying lots of luggage upfront, I can use a lower tyre pressure).

For interest, I'll probably end up trying the 27.5" Front wheel after seeing how this current set up handles for a few months.


While theoretically this might all make sense; on my E bike which I use for commuting with moderate load. I've got 27.5 inch wheels front and back but a much wider front tire.
2.35" at the back and 2.8 at the front"

Since making this change to a much wider front tire on the E bike the handling has felt much more stable and giving me a lot more confidence on my commute. (about 15 miles each way half of which is off-road on relatively rough tracks)

However, I did make other changes to the E bike at the same time, such as bamboo handlebars and a redshift suspension stem.

Will report back in a few months once I've made a comparison.

Ewan

Andyb1

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #8 on: May 22, 2024, 09:26:28 am »
My personal experience is that an easy way to inadvertently upset a bike’s stability is to fit a handlebar bag.   Without rear panniers it upsets the bike in a X-wind and it’s weight forward of the handlebar stem makes the bike more twitchy as the bag’s weight increases.   Longer mounts that move the bag further forwards must make these effects worse.

I have never tried having a bag on a rack on top of the front wheel but I imagine this might cause the same problems?

I have only been (occasionally) using a handlebar bag for about a year and while it is a useful place for valuables etc I always keep the weight to a minimum.

By comparison I can not feel any negative handling effects with the tyre on the front 1/4 inch bigger than on the rear.

 

Andre Jute

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #9 on: May 22, 2024, 11:57:05 pm »
My personal experience is that an easy way to inadvertently upset a bike’s stability is to fit a handlebar bag.   Without rear panniers it upsets the bike in a X-wind and it’s weight forward of the handlebar stem makes the bike more twitchy as the bag’s weight increases.   Longer mounts that move the bag further forwards must make these effects worse.

I have never tried having a bag on a rack on top of the front wheel but I imagine this might cause the same problems?

You're absolutely right. Most cyclists with their brain in gear try to distribute the weight on a loaded bike equally between the wheels whether they know about the Centre of Gravity and the dynamic couple between the front and rear wheels or not. It's long-established common sense.

But very few know about another movable point, called the Centre of Aerodynamic Pressure, which acts, to simplify matters, through the side profile of the bike, which makes the distribution of surfaces extremely important because it is imperative for the stability of any vehicle that the centre of aerodynamic pressure be behind the centre of gravity.

If you contemplate the side surfaces of the front of the bike and of the rear, you will see that with the rider on board there is just about zero chance of the centre of aerodynamic pressure moving forward. Panniers are put first on the back for a good reason, so is any further loading of the rack. The height of any load with much surface at all also goes on the rear rack first rather than the front, and lowrider pannier are fitted low down because you don't want the dynamic centre of aero pressure to slope downwards towards the back of the bike.

If the cyclist as his only load on the bike except himself fits a rack bag and high up at that, he unsettles the distribution of side surfaces and the stability of the bike in side winds as small as that caused by a hatchback passing him. The bike wants to swap ends because it is quite possible that in addition the front to rear aero couple now runs downwards.

That's what your experienced. Note that in yaw all these forces (vectors) may be ameliorated or enhanced. A good example is a large flat side truck passing close by. With the bike's design side surface and consequently aero handling upset by a possible doubling of the front surface by the rack bag, a point may arrive where you don't know which way the front wheel will break, which adds another layer of uncertainty.

Once, at a crossroad with high hedges on all sides, a gust of wind knocked me off my bike. A trucker stopped and helped me (I hurt a lot -- I'd been travelling at speed) and said, "You're not a blow-in [a recent arrival in the countryside]. You should know better. All the flatsiders [closed truck drivers] know about this corner." I'd been riding there thirty years. I hadn't even thought of the aero CoP because a lot of the aero effects I was used to in motor racing don't matter with a four-wheel vehicle until you're travelling well over the ton and you anyway have large flat surfaces well behind the rear axle. I calculated up the side areas on my bike and instantly discovered that a handlebar bag, while very convenient, is an invitation to road rash in a windy area such as I live in on the River Bandon.

Jobst Brandt, probably the leading theoretician of bikes in the latter half of the 20th century, used to say, "If the front wheel goes, there's nothing you can do. You're gone." It's one reason the centre of pressure and reaction to invisible side forces like crosswinds must remain behind the centre of gravity of the bike under all dynamic conditions, because you can recover from a rear-end upset whereas at the front recovery falls somewhere between extremely difficult and goodbye.

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By comparison I can not feel any negative handling effects with the tyre on the front 1/4 inch bigger than on the rear.

That's hardly surprising; it's a modest change, well within the design parameters for any competent touring bike, which has large reserves of dynamic safety built in. But make the front much wider than the rear, and take the bike out on a fast downhill with curves, and you'll frighten yourself. A bike that turns in sweetly at moderate speed in rush hour traffic will suddenly become a health hazard. And worse with a touring load on it.

For a while, because I just couldn't find a wide rim (24mm across the beads, minimum) actually in stock anywhere, I used a motor built into a narrow front rim with the fat tyre on the fat rim with the Rohloff at the rear. On hilly lanes I'd been riding for decades, it was pretty obvious that the bike was nervous enough for me to cut apex speed from 55kph on the sweeping downhill curves to just over 30kph because the 60mm Big Apples just weren't working the same predictable way any more. Until then I'd declared the difference in the rims "not such a big deal", which was true enough when the referring to riding on the level under 20kph. It was one reason that for my next venture into electrifying the bike, I bought a mid-motor, to move the weight and the motor aero area backwards and downwards -- and to return to my fabulous 24mm rim width all round.

Andyb1

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #10 on: May 23, 2024, 08:55:06 am »
A simple example of how to achieve good aerodynamic stability are the fins on the rear of a dart.   You can not throw a dart backwards!

I also found how badly the WEIGHT of the handlebar bag effected the bike’s stability.  Particularly at slower speeds.  Yet gravel riders seem happy to carry large bags strapped to the handlebars……

Before touring in India I tried riding with different loads in my Carradice Super C handlebar bag (which with mount weighs close to 1kg), without rear panniers, on a calm day.  It is rated to carry 7kg but anything over 2kg in it made the bike unpleasant.  This was on a rigid MTB which already had much faster (twitchy) handling than a touring frame.  The only solution I could come up with was to fit slightly wider straight handlebars than those I normally use, to give me a bit more control.

By comparison my Sherpa will cope fine with +2kg in the same bag with narrower handlebars - but it has a much more stable fork geometry.

in4

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #11 on: May 24, 2024, 01:59:48 pm »
Using an Ortlieb bar bag. I try to keep the weight down to a minimum. Usually glasses, keys, headtorch; small stuff. On the odd occasion I put my phone in it I try to place it in 'landscape' position and as near to the steerer as possible. Too much weight in the bar bag makes it move up and down, especially when I'm climbing in a low gear. Also it makes the steering less 'sure' particularly when using a T bar. I think my bar bag is an Ultimate model er, 6 litre. I'll get a map case to sit on top of it one of these days.
In short, I've found a bar bag ( attached to a T bar) very useful for putting small essentials in plus its easy to remove when necessary ( going into a store for example )

PH

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #12 on: May 25, 2024, 07:36:39 pm »
Every action has a reaction, but I think the arguments on both sides of this one are over reactions.  I rode Derby > Barcelona some years ago, set off on a pair of  30mm Marathon Racers and split the rear before leaving the UK, choice in the first Decathlon in France was 25mm or 40, nothing in between and I bought the larger.  That wouldn't fit the frame so the bigger tyre went on the front.  That's a difference in radius of 10mm.  Did it feel different? Yes.  Was it a problem? No. 50 miles later I'd forgotten about it, not only did I not go looking for another tyre in the remaining 900 miles, I didn't bother swapping it when I go home.
Gratuitous photo, spot the difference


A 27.5" rim has a 25mm larger diameter than a 26" (584 V's 559), 3.5%, a radius difference of 12.5mm.  Form your own opinion about the effect that might have, or better still try it yourself.

Opinions on bar bags also vary, though you have to factor in familiarity.  I nearly always ride with one, out of laziness it'll sometimes hold a 2kg chain lock as well as the other stuff, the only time I consider it an issue is when off the bike it makes the bars flop.  The weight difference with/without the bag will be less than the difference in weight distribution between grips and bar ends on a straight bar, or tops and hoods on drop bars.  Your choice of course, though it makes me laugh that many Audax riders who wouldn't have considered one a decade ago, now wouldn't be without.

« Last Edit: May 25, 2024, 07:41:15 pm by PH »

martinf

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #13 on: May 26, 2024, 07:06:53 am »
Opinions on bar bags also vary, though you have to factor in familiarity.

I used a bar bag for quite a long time in the 1970's, but never really liked it. Perhaps because the frames I had at the time were closer to race geometry than for stable touring.

One advantage of a bar bag is that it can be quickly removed.

For day rides I got a bigger saddlebag to replace the volume lost by removing the bar bag, and a quick release fitting so that I could take all my luggage with me except water bottles and, at that time, a frame fitting pump.

For longer tours with pannier bags I use a small rucksack. I put all the valuable items in that and it goes in one of the panniers. Perhaps not quite so quick as a handlebar bag, and less convenient if I want to take photos, but more useful if I want to take a walk in the evening after parking the bike somewhere.
« Last Edit: May 26, 2024, 04:59:36 pm by martinf »

mickeg

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Re: Mullet nomad mk 2 (26" rear -- 27.5" front)
« Reply #14 on: May 26, 2024, 11:07:03 am »
...
Since making this change to a much wider front tire on the E bike the handling has felt much more stable and giving me a lot more confidence on my commute. (about 15 miles each way half of which is off-road on relatively rough tracks)
...

A rotating wheel is like a gyroscope, resists wanting to change orientation.  The faster it spins and the heavier it is, the stronger that resistance to change in orientation.  I can see where a heavier tire on the front can give a feeling of stability.

If I put really light wheels with skinny light weight tires on a bike, the steering is more sensitive, same with my folding bike with smaller diameter tire.

I am not saying that caused all the change, but I am sure it contributed to it.